Showing papers in "Endocrinology in 1979"
TL;DR: It is shown that euthyroid calf serum depleted of L-T3 andL-T4 by this procedure yields serum which, when used as a medium supplement, results in biological responses identical to those obtained with media supplemented with thyroidectomized calf serum.
Abstract: GH1 cells are a clonal strain of rat pituitary tumor cells which synthesize GH and PRL. We have previously demonstrated that these cells respond to physiological concentrations of L-T3 and L-T4 when cultured with medium supplemented with thyroidectomized calf serum to achieve a thyroid hormone-depleted state under cell culture conditions. In this study, we describe a method to deplete euthyroid calf serum of L-T3 and L-T4 using an anion exchange resin. We demonstrate that the procedure only minimally alters the low molecular weight anion components of the serum and does not change the total protein content or the electrophoretic pattern of serum proteins. Moreover, we show that euthyroid calf serum depleted of L-T3 and L-T4 by this procedure yields serum which, when used as a medium supplement, results in biological responses identical to those obtained with media supplemented with thyroidectomized calf serum. In addition, resin treatment does not alter the growth-promoting properties of the serum if the thyroid hormone concentration is restored. This procedure should be useful in preparing thyroid hormone-depleted serum for cell culture studies in situations where thyroidectomy is not feasible or would require surgical procedures on a large number of small animals.
643 citations
TL;DR: Sequential blood samples were obtained from undisturbed, unrestrained, male and female rats of different ages from intrajugular or intraaortic cannulae implanted 4 days before experimentation and plasma GH was determined by RIA.
Abstract: Sequential blood samples were obtained from undisturbed, unrestrained, male and female rats of different ages from intrajugular or intraaortic cannulae implanted 4 days before experimentation. Blood (70–100 μl) was gently withdrawn at 30-min intervals for periods of 6 h. Plasma GH was determined by RIA. In 22-day-old rats, episodic secretion of GH was evident, but plasma GH levels did not exceed 70 ng/ml. In older rats, peak levels of GH were higher and there was a significant difference in the secretory pattern of GH between male and female rats. In male rats, 30, 45, and 90 days old, GH surges in individual animals occurred at regular 3- to 4-h intervals. Peak levels were 200-300 ng/ml and levels between peaks, were mostly <5 ng/ml. The timing of the peaks with respect to clock time was similar in most animals. In 30-day-old rats, peak levels were lower in females than in males. In 45-day-old female rats, GH was secreted episodically, and peak levels were 200-300 ng/ml. However, the interval between pea...
534 citations
TL;DR: Insulin-binding sites were localized in the rat brain by means of light microscopic radioautography and the radioautographic reactions over the circumventricular organs, the medial basal hypothalamus, and the paravagal region were reduced, indicating the presence of competitive binding sites.
Abstract: Insulin-binding sites were localized in the rat brain by means of light microscopic radioautography. Male rats were injected intracardially with [125I]iodoinsulin in the absence and presence of excess unlabeled insulin, insulin analogs, or structurally unrelated polypeptide hormones. Five minutes after injection, the brains were preserved in vivo by perfusion and subjected to radioautographic procedures. Radioautographic reactions caused by [125I]iodoinsulin occurred over all circumventricular organs lacking a blood-brain barrier. In addition, the medial basal hypothalamus, the medial paravagal region, and the choroid plexus were labeled. In the presence of a 500-fold excess of coinjected unlabeled insulin, the radioautographic reactions over the circumventricular organs, the medial basal hypothalamus, and the paravagal region were reduced by 56–78%, indicating the presence of competitive binding sites. In the external contact zone of the median eminence and in the hypothalamic arcuate nucleus, the effect...
327 citations
TL;DR: The results of these studies suggest that endogenous opioids exist in brain tissue which normally inhibit activity in the hypothalamic-pituitary-LH axis and participate in the androgen-dependent feedback control of LH elaboration by this axis.
Abstract: Two narcotic antagonists, naloxone and naltrexone, significantly elevated serum LH levels in male rats within minutes after their sc injection. The peak increase in serum LH occurred 20 min after the injection. Naloxone increased LH levels up to a dose of 1 mg/kg, after which no further increases were found. A dose of 0.35 mg/kg produced a half-maximal response. The exogenous opioid morphine blocked the increase in LH produced by naloxone in a dose-dependent fashion, suggesting that the specific receptor-blocking effects of the antagonist could account for its enhancement of serum LH levels. The locus of action of naloxone within the hypothalamic-pituitary-LH axis appeared to be at the level of the hypothalamus since the drug had no effect on LHRH-stimulated release of LH by the anterior pituitary and did not block dihydrotestosterone's suppression of pituitary LH release in vitro. Naloxone also prevented testosterone's negative feedback inhibition of serum LH in the castrated male rat. The results of the...
319 citations
TL;DR: Release of radioimmunoassayable LHRH from hypothalamic fragments of adult male rats was measured using an in vitro incubation system and increased release from the ME, was 10 to 15-fold higher than that from the MBH or theMBH-ME unit.
Abstract: Release of radioimmunoassayable LHRH from hypothalamic fragments of adult male rats was measured using an in vitro incubation system. Each flask, containing three tissue fragments in 0.5 ml Krebs-Ringer bicarbonate glucose buffer, was incubated for 15 min, followed by a 30-min incubation during which either basal release or the effect of catecholamines on LHRH output was evaluated. In some cases, tissues employed consisted of a fragment of medial basal hypothalamus which included the median eminence (ME), the arcuate and ventromedial nuclei, and surrounding structures (MBH-ME unit). In other experiments, the ME was separated from the rest of the MBH by a rnicrodissection procedure and both fragments were incubated in separate flasks. Basal LHRH release from the different fragments was readily detectable, during both the preincubation and incubation periods. LHRH release from the ME, was 10 to 15-fold higher than that from the MBH or the MBH-ME unit. This increased release from the ME was not due to a diff...
269 citations
TL;DR: It is concluded that electrolytic VMH destruction causes immediate hypersecretion of the pancreatic B cell, an effect that requires the integrity of the vagus nerves.
Abstract: The acute effect of bilateral electrolytic ventromedial hypothalamic lesions (20–25-m Coulomb stainless steel electrodes) on plasma levels of insulin and glucose was studied in anesthetized rats to determine early effects that would occur before hyperphagia and obesity. In rats fed ad libitum, lesions in the ventromedial hypothalamus (VMH) but not in the cortex produced a marked increase in circulating insulin levels (starting at 20 min postlesion) and a small increase in glycemia which, however, was not significant and could therefore not be the cause of increased insulin secretion. Hyperinsulinemia after VMH lesions was more pronounced when glucose was infused iv at a rate of 7–8 mg/kg-min. Bilateral subdiaphragmatic vagotomy, performed 50 min after VMH lesions, immediately and completely reversed the observed hyperinsulinemia. With the exception of a tendency of lesions producing the highest degree of hyperinsulinemia to be slightly larger than the lesions not producing any hyperinsulinemia, no stateme...
269 citations
TL;DR: It is suggested that NT acts centrally to inhibit LHRH release and to bring about an inhibition of PRL release and that it can be enhanced with doses of 50 or more ng/ml medium.
Abstract: Conscious ovariectomized rats bearing a cannula implanted in the third ventricle were injected with 2 μl 0.9% NaCl containing varying doses of substance P (SP) or neurotensin (NT), and plasma gonadotropins and PRL were measured by RIA of jugular blood samples drawn through an indwelling silastic catheter. Control injections of saline iv or into the thirdventricle did not modify plasma hormone levels. Intraventricular injection of NT at doses of either 0.5 or 2 μg lowered plasma LHconcentrations within 5 min and they remained low for 60 min. These doses of NT also lowered plasma PRL with a similar time course. An intermediate dose of 1 μg NT iv had no effect on plasma LH but elevated plasma PRL. Incubation of hemipituitaries from OVX rats with varying doses of NT did not alter gonadotropin release into the medium, but PRL release was enhanced with doses of 50 or more ng/ml medium. It is suggested that NT acts centrally to inhibit LHRH release and to bring about an inhibition of PRL release and that it can ...
249 citations
TL;DR: It is demonstrated that the mitogenic effects of EGF and FGF are not restricted to granulosa cells of bovine origin and, with the exception of rat granULosa cells, cultured granul Rosa cells responded either to FGF alone or to both EGFand FGF with a marked increase in their rates of proliferation.
Abstract: The mitogenic effects of epidermal growth factor (EGF) and fibroblast growth factor (FGF) on cultured granulosa cells of different species have been analyzed. EGF and FGF are potent mitogenic agents for rabbit, porcine, and human granulosa cell cultures. While guinea pig granulosa cell cultures respond to FGF, they were hardly effected by EGF. Rat granulosa cell cultures did not respond markedly to either EGF or FGF. Our results, therefore, demonstrate that the mitogenic effects of EGF and FGF are not restricted to granulosa cells of bovine origin and, with the exception of rat granulosa cells, cultured granulosa cells responded either to FGF alone or to both EGF and FGF with a marked increase in their rates of proliferation.
242 citations
TL;DR: Ovariectomized conscious rats bearing chronically implanted third ventricular cannula were injected with varying doses of vasoactive intestinal peptide, and plasma LH, PRL, GH, TSH, and FSH levels were measured by RIA in jugular blood samples drawn through an indwelling silastic cannula.
Abstract: Ovariectomized conscious rats bearing chronically implanted third ventricular cannula were injected with 2 μl 0.9% NaCl or 2 μd saline containing varying doses of vasoactive intestinal peptide (VIP), and plasma LH, PRL, GH, TSH, and FSH levels were measured by RIA in jugular blood samples drawn through an indwelling silastic cannula. Control injections of saline iv or into the third ventricle did not modify plasma hormone levels. Third ventricular injection of 4, 40, and 100 ng VIP produced a significant elevation within 5 min in plasma LH, while PRL levels were elevated only by 40- and 100-ng doses; however, the highest dose of 500 ng had no effect on plasma LH or PRL levels. Plasma GH titers increased significantly after third ventricular injection of each dose of VIP at 15 min and remained elevated for the duration of the experiment. Intravenous injection of VIP at doses of 40 and 1000 ng had no effect on plasma LH, but PRL levels were significantly elevated by the 1000-ng dose. Plasma GH was not odifi...
234 citations
TL;DR: Analysis of the role of calcium in the regulation of aldosterone production showed that the steroidogenic responses of isolated adrenal cells to ACTH, angiotensin II, and potassium were highly dependent on the extracellular calcium concentration.
Abstract: Analysis of the role of calcium in the regulation of aldosterone production showed that the steroidogenic responses of isolated adrenal cells to ACTH, angiotensin II, and potassium were highly dependent on the extracellular calcium concentration. Physiological concentrations of calcium were required for maximal aldosterone responses to all three regulators, and steroidogenesis was progressively reduced by decreasing calcium concentrations. ACTH stimulated aldosterone and cAMP responses at all calcium concentrations tested, and the production of steroid was correlated with the increase in cAMP formation. Reduction of extracellular calcium concentration caused an increase in the ACTH concentration required for halfmaximal steroid and cAMP production and a decline in the maximal output of aldosterone. When zona glomerulosa cells were stimulated by exogenous cAMP, cholera toxin, or serotonin, decreased calcium concentration caused a decline in the amount of steroid produced but did not change the agonist conc...
231 citations
TL;DR: The synthetic radiolabeled androgen methyltrienolone-17βhiydroxy-17α-methyl-estra-4,9,ll-trien-3-one (R1881) is superior to the native ligand 5α-dihydrotestosterone (DHT) in the measurement of androgen receptor (AR), especially in tissues where radiolabelled DHT binds with high affinity to plasma proteins in addition to receptor.
Abstract: The synthetic radiolabeled androgen methyltrienolone-17βhiydroxy-17α-methyl-estra-4,9,ll-trien-3-one (R1881) is superior to the native ligand 5α-dihydrotestosterone (DHT) in the measurement of androgen receptor (AR), especially in tissues where radiolabeled DHT binds with high affinity to plasma proteins in addition to receptor or is rapidly metabolized to inactive derivatives. However, R1881 also binds progesterone receptor (PgR), as shown by its ability to complete for [3]-promestone-17α,21-dimethyl-19-nor-pregna-4,9-diene-3,20-dione (R5020) binding to 8S PgR on sucrose density gradients, resulting in an overestimation of AR if PgR is present. Therefore, we have devised a method by which PgR binding of R1881 can be blocked without interfering with AR binding. The glucocorticoid triamcinolone acetonide (TA) was found to bind PgR (competition for 8S [3]R5020 binding) but not AR (no competition for 8S [3H]DHT binding). In cytosols containing both receptors, a 500-fold excess of unlabeled TA was sufficient ...
TL;DR: The effects of prolonged food deprivation on plasma GH, pituitary GH, and tissue somatostatin levels were investigated in the male rat and a rebound response was observed in rats allowed to refeed for 3 days after 72-h food deprivation, as evidenced by an increased number of GH secretory episodes and a shorter period of the GH rhythm.
Abstract: The effects of prolonged food deprivation on plasma GH, pituitary GH, and tissue somatostatin levels were investigated in the male rat. Six-hour GH secretory profiles obtained from normal animals bearing chronic intracardiac venous cannulae showed the typical ultradian GH rhythm, with most peak GH values being >600 ng/ml. Exposure to 24-h food deprivation resulted in a significant depression in amplitude of GH pulses, with peak values not exceeding 300 ng/ml. The amplitude and duration of the GH secretory episodes declined progressively after 48 and 72-h food deprivation, and normal periodicity was not evident. The mean 6-h GH level in each of the food-deprived groups was significantly less than that of normal animals. A rebound response was observed in rats allowed to refeed for 3 days after 72-h food deprivation, as evidenced by an increased number of GH secretory episodes and a shorter period of the GH rhythm. In a second series of experiments, pituitary GH and tissue levels of somatostatin-like immuno...
TL;DR: High affinity binding of melatonin in crude membrane preparations of bovine brain was examined by a rapid filtration procedure through Whatman GFB paper and melatonin binding was maximal in the MBH; indole binding in occipital and cerebellar cortexes was 73% and 34% that of MBH.
Abstract: High affinity binding of melatonin in crude membrane preparations of bovine brain was examined by a rapid filtration procedure through Whatman GFB paper. Melatonin binding to medial basal hypothalamic (MBH) membranes attained its maximum at the first, third, and fifth hours of incubation at. 37,18, and 0 C, respectively. Specific binding was linear up to 3 mg membrane protein, was thermolabile, and decreased after incubation with trypsin; it was also pH dependent, the maximum being observed at pH 7.4. Melatonin binding was affected by a variety of ionic manipulations; it was inhibited 55% and 62% after addition of 10 mM KC1 and 120 mM NaCl, respectively, and it was increased 40% and 50% after the addition of 4 or 6 mM CaCl2. Melatonin binding was increased 25% by 1.25 mM MgCl2, whereas it was depressed at higher concentrations. Among the various brain regions studied, melatonin binding was maximal in the MBH; indole binding in occipital and cerebellar cortexes was 73% and 34% that of MBH. Subcellular frac...
TL;DR: A RIA for chick intestinal calcium-binding protein (CaBP) has been developed with a sensitivity of 1 ng and showed a good correlation with measurements of CaBP by the radial immunodiffusion method.
Abstract: A RIA for chick intestinal calcium-binding protein (CaBP) has been developed with a sensitivity of 1 ng. The antiserum was generated in rabbits injected with highly purified vitamin D-dependent chick intestinal CaBP. The assay employs the double antibody technique, and 125-labeled CaBP was prepared using chloramine T. Low molecular weight peptide hormones and normal rabbit, rat, and human serum proteins show no cross-reactivity in the assay. Measurements of chick intestinal and kidney CaBP by RIA showed a good correlation with measurements of CaBP by the radial immunodiffusion method. The assay is reproducible (interassay variability, 16.3%) and precise (intraassay variability, 4.0%). The concentration of immunoreactive CaBP (iCaBP) in chick serum (2.7 ng/ml serum) can now be measured as early as 8 h after the administration of 6.5 nmol 1,25-dihydroxyvitamin D3; a maximum of 11 ng/ml is reached at 20 h. The level of CaBP in chick serum was found to be dependent on the dose of vitamin D3 or 1,25-dihydroxyv...
TL;DR: This study investigates the direct estrogen receptor interactions and the character of the biological activities of three estrogenic resorcylic acid lactones in the immature rat uterus of fungal metabolites associated with estrogenizing syndromes in cattle fed mold-infected grain.
Abstract: This study investigates the direct estrogen receptor interactions and the character of the biological activities of three estrogenic resorcylic acid lactones in the immature rat uterus. These compounds are fungal metabolites (P-1492; zearalenone) or derivatives thereof (P-1496 and P-1560; epimeric zearalanols) that have been associated with estrogenizing syndromes in cattle fed mold-infected grain. The compounds compete with estradiol for binding to the cytoplasmic receptor (P- 1496, 13.6%; P-1492, 1.8%; P-1560, 0.8% that of estradiol), and they translocate estrogen receptor sites to the nucleus, with P- 1496 showing the most prolonged nuclear receptor interaction. The three compounds induce the synthesis of the uterine induced protein (P-1496 > P-1560 > P-1492) and increase uterine weight. Direct binding studies with the most potent compound P-1496, in tritium-labeled form indicates a Kd of 1.8 nM (compared to 0.12 nM for estradiol) for interaction with uterine cytoplasmic receptor. Cytoplasmic receptor ...
TL;DR: The molecular nature of immunoreactivity in parathyroid venous blood, which was collected from anesthetized calves by surgical cannulation, was examined by gel filtration and RIAs with specificity for either the amino (N assay) or carboxyl end of the hormone molecule.
Abstract: The molecular nature of immunoreactivity in parathyroid venous blood, which was collected from anesthetized calves by surgical cannulation, was examined by gel filtration and RIAs with specificity for either the amino (N assay) or carboxyl (C assay) end of the hormone molecule. All samples contained immunoreactivity which eluted from the gel column (Bio-Gel P-100; 45 × 1.2 cm) coincident with radioiodinated purified parathyroid hormone (84 amino acids). This material reacted in both N and C assays. In addition to this, the effluent plasma immunoreactivity contained another component which eluted from the column after the radiolabeled hormone and was recognized only by the C assay. Very little of the latter type of material was found in hypocalcemic samples, but it represented an increased proportion of the total immunoreactivity in normocalcemic samples and this material was the predominant form of immunoreactivity in hypercalcemic samples. RIA of a series of samples of parathyroid venous plasma, collecte...
TL;DR: The data support the conclusion that bombesin acts within the brain to increase sympathetic outflow resulting in increased adrenalmedullary epinephrine secretion, followed by depression of plasma insulin and elevation of plasma glucagon and glucose.
Abstract: Bombesin acts within the brain to produce a prompt and sustained hyperglycemia, hyperglucagonemia, and relative or absolute hypoinsulinemia. Bombesin does not decrease plasma glucose turnover. Acute adrenalectomy but not hypophysectomy prevents hyperglycemia and hyperglucagonemia after intracisternal administration of bombesin. Administration of bombesin into the lateral ventricle of awake, unrestrained animals results in elevation of plasma glucose, preceded by a significant increase in plasma epinephrine and no increase in plasma norepinephrine or dopamine. Systemic administration of somatostatin prevents bombesin-induced hyperglycemia and hyperglucagonemia. These data support the conclusion that bombesin acts within the brain to increase sympathetic outflow resulting in increased adrenalmedullary epinephrine secretion, followed by depression of plasma insulin and elevation of plasma glucagon and glucose.
TL;DR: The data suggest that significant between-species variation of T production in response to ovine LH is not due to quantitative differences in the mass of Leydig cells, as determined by morphometric analysis.
Abstract: Stereological methods were employed to determine volume and surface densities of cytoplasmic organelles in Leydig cells of hamster, rat, rabbit, dog, and guinea pig testes. Contralateral testes were perfused in vitro with maximally stimulating gonadotropin concentrations to determine the capacity of these testes to secrete testosterone. Significantly different amounts of testosterone were secreted by in vitro perfused testes of the five species when maximally stimulated with ovine LH. Significant differences also were seen in the volume and surface densities of smooth endoplasmic reticulum, mitochondria, rough endoplasmic reticulum, and lipids in Leydig cell cytoplasm of the five species. Most interestingly, linear positive correlations were seen between testosterone secretion and smooth endoplasmic reticulum volume (r = 0.99) and surface (r = 0.99) densities. Thus, virtually all of the differences in testosterone secretion by maximally stimulated testes of five species could be accounted for by between-s...
TL;DR: Use of these analogs as both the labeled and unlabeled ligand offers substantial advantages over GnRH for investigation of GnRH receptors, allowing accurate determination of changes in their numbers and affinities under various physiological conditions.
Abstract: Studies of pituitary plasma membrane gonadotropin- releasing hormone (GnRH) receptors using [I25I]- iodo-GnRH suffer major disadvantages. Only a small (<25%) proportion of specific tracer binding is to high affinity sites, with more than 70% bound to low affinity sites (Ko = 1 X 106 M'). [l25I]Iodo-GnRH is also inactivated during incubation with pituitary plasma membrane preparations. Two superactive analogs of GnRH, substituted in positions 6 and 10, were used as the labeled ligand to overcome these problems. Both analogs bound to the same high affinity sites as GnRH on bovine pituitary plasma membranes, though the affinity of the analogs was higher than that of the natural decapeptide (Ka s 2.0 x 109, 6.0 x 109, and 3.0 x 108 M“1 for [D-Ser(TBu)6]des-Gly10-GnRH ethylamide, [D-Ala6]des-Gly10-GnRH ethylamide, and GnRH, respectively). The labeled analogs bound to a single class of high affinity sites ith less than 15% of the specific binding being to low affinity sites (Ka S 1 X 1 0 6 M “ ‘). The labeled n...
TL;DR: The effects and binding of insulin-like growth factor-I in skeletal muscle were investigated in the isolated mouse soleus muscle from normal lean and goldthioglucose- obese mice and a specific binding of [125I]iodo-IGF-I was observed, which was not inhibited by unlabeled insulin or proinsulin.
Abstract: The effects and binding of insulin-like growth factor-I (IGF-I) in skeletal muscle were investigated in the isolated mouse soleus muscle from normal lean and goldthioglucose- obese mice. In muscles from lean mice, IGF-I stimulated 2-deoxyglucose uptake, glycolysis, and glycogen synthesis and activated glycogen synthase. The latter effect occurred in the absence of glucose in the incubation medium, as was also observed with insulin. The maximal effects of IGF-I and insulin on 2-deoxyglucose uptake were not additive. IGF-I was about 4–9% as potent as insulin (half-maximal effects occurred with 5-14 nM IGF-I) and nearly as effective as insulin. A specific binding of [125I]iodo-IGF-I was observed, which was not inhibited by unlabeled insulin or proinsulin. IGF-I was less than 1% (on a molar basis) as potent as insulin in competing with [125I]iodoinsulin binding. Unlike [125I]iodoinsulin binding, [125I]iodo-IGF-l binding was similar in muscles from lean and goldthioglucose-obese mice. As observed with insulin,...
TL;DR: The hormonal regulation of testicular aromatization and the intratesticular site of estradiol synthesis was investigated in adult rats and cell-free homogenates of whole testes, isolated interstitial tissue, and seminiferous tubules were incubated with [3H]testosterone.
Abstract: The hormonal regulation of testicular aromatization and the intratesticular site of estradiol synthesis was investigated in adult rats. To determine testicular aromatization, cell-free homogenates of whole testes, isolated interstitial tissue, and seminiferous tubules were incubated with [3H]testosterone. 3H-Labeled estrogens were isolated and final identity was established by recrystallization of the product with authentic 17β-estradiol or estrone. No 3H-labeled estrogens could be identified in testicular incubations from saline-treated rats. In contrast, similar incubations from rats treated for 6 days with hCG or LH had the capacity to aromatize testosterone to estradiol. Testicular homogenates from rats treated with 4.4 IU hCG/day synthesized 4.76 pg estradiol/mg protein, which represents approximately 280 pg estradiol synthesized/testis during a 3-h incubation. In incubations of cell-free homogenates of isolated testicular compartments from hCG-treated rats, aromatase activity was demonstrated only i...
TL;DR: In an attempt to localize estrogen-sensitive brain sites sufficient to prime feminine sexual behavior, 30-gauge cannulae containing approximately 9 ng high specific activity [3H]-estradiol were implanted unilaterally or bilaterally into the ventromedial region of the hypothalamus of ovariectomized rats.
Abstract: In an attempt to localize estrogen-sensitive brain sites sufficient to prime feminine sexual behavior, 30-gauge cannulae containing approximately 9 ng high specific activity [3H]-estradiol were implanted unilaterally or bilaterally into the ventromedial region of the hypothalamus of ovariectomized rats. Tests for lordosis behavior were conducted on days 3 and 6 postimplantation, 4–6 h after progesterone treatment. Brain, pituitary, and uterine tissue were then sampled for radioactivity. Cannulae delivered, on the average, 3 ng [3H]estradiol during 8 days. Radioactivity was localized almost exclusively to the hypothalamus or hemihypothalamus in which the implant was placed. This was true regardless of whether tissue radioactivity or radioactivity in cell nuclei was analyzed. In the bilateral implant experiments, average hypothalamic [3H]estradiol radioactivity amounted to 56 pg/rat in tissue and 220 fg in purified cell nuclei. The latter is 4% of the estimated estrogen eceptor capacity of cell nuclei of th...
TL;DR: The stimulatory effect was seen at high and low concentrations of unlabeled proline and was not associated with increased incorporation of [3H]thymidine into DNA or [ 3H]uridine into RNA; release of labeled collagen from bone to medium was unaffected by cortisol.
Abstract: Effects of glucocorticoids on bone collagen synthesis were examined in organ cultures. Fetal rat calvaria were incubated with [3H]proline during the last 2 h of culture; [3H] proline incorporation into collagenase-digestible (CDP) and noncollagen protein (NCP) was measured using purified bacterial collagenase. Cortisol (0.03-3 μM) increased incorporation of label after 24 h, although CDP was affected more than NCP. Cortisol did not alter collagen synthesis in freshly explanted bones cultured for 3 h. The stimulatory effect was seen at high and low concentrations of unlabeled proline and was not associated with increased incorporation of [3H]thymidine into DNA or [3H]uridine into RNA; release of labeled collagen from bone to medium was unaffected by cortisol. Dexamethasone (9α-fluoro- 11β,17α,21-trihydroxy- 16α-methylpregna- l,4-diene-3,20-dione; 1 nM), corticosterone, and cortexolone (17α,21-dihydroxy-4-pregnene- 3,20-dione; 0.1 μM) increased collagen synthesis after 24 h; epicortisol (11α,17α,21-trihydro...
TL;DR: The differential stimulation of type II sites by estradiol and estriol suggests that this is a specific estrogenic response and is highly correlated with uterine growth.
Abstract: Estradiol administration causes an increase in two specific binding components in uterine nuclei of mature ovariectomized rats. One of these sites (type I) represents the estrogen receptor which binds estradiol with high affinity (dissociation constant, 1 nM) and low capacity (1 pmol/uterus) and is translocated from the cytoplasm to the nucleus. The second component (type II) binds estradiol with a higher capacity than type I sites and displays a saturation curve which is sigmoidal. Hence, no accurate estimation of the dissociation constant can be made. The differential stimulation of type II sites by estradiol and estriol suggests that this is a specific estrogenic response and is highly correlated with uterine growth. A single injection of estradiol results in long term retention of type I sites (>6 h), rapid and sustained elevations of type II sites (1-72 h), and true uterine growth. In contrast, estriol injection caused a rapid increase in type I sites which was not accompanied by an increase in typ e...
TL;DR: The hypothesis was tested that a decrease in response to the inhibitory feedback action of estradiol on tonic LH secretion occurs in the female lamb during puberty, and the first ovulation in intact lambs occurred over a wide range of body weights.
Abstract: The hypothesis was tested that a decrease in response to the inhibitory feedback action of estradiol on tonic LH secretion occurs in the female lamb during puberty. Ovaries were removed from 10 female lambs at 19 weeks of age, which was approximately 11 weeks before the expected first ovulation. At ovariectomy, Silastic implants containing crystalline estradiol were inserted sc in 6 lambs to maintain chronic low levels of circulating estradiol. In estradiol-treated ovariectomized lambs, serum LH was suppressed to undetectable concentrations until the age when first ovulations were initiated in untreated intact lambs. At this time, circulating LH increased dramatically to castrate levels in 5 of 6 estradiol-treated ovariectomized females despite maintenance of constant levels of serum estradiol. The ”escape“ from estradiol negative feedback on tonic LH secretion in ovariectomized lambs and the first ovulation in intact lambs occurred over a wide range of body weights. In the slowest growing estradiol-treat...
TL;DR: Efficient dissociation of bound PRL could be obtained with 1.6–4 M ammonium thiocyanate and 4 M sodium trifluoroacetate, although MgCl2 was far superior in the rebinding studies, indicating some irreversible damage to the receptor by some of the dissociating agents.
Abstract: [125I]Iodoovine PRL ([125I]oPRL) binds with high affinity and specificity to crude membrane fractions prepared from either rabbit mammary gland or female rat liver. After completion of [125I]iodo-PRL binding, a short (5-min) exposure to magnesium chloride (4–5 M) resulted in a 91–97% dissociation of the bound [125I]iodo-PRL. Upon reincubation with fresh [125I]iodo-PRL in the absence or presence of 1 μg unlabeled oPRL, the membrane preparation specifically bound 89–105% of the label bound by control (H2O-treated) membranes. Similar results were observed with 4 M MnCl2. Efficient dissociation of bound PRL could also be obtained with 1.6–4 M ammonium thiocyanate and 4 M sodium trifluoroacetate, although MgCl2 was far superior in the rebinding studies, indicating some irreversible damage to the receptor by some of the dissociating agents. Similar positive results were obtained by first saturating he binding sites with unlabeled PRL, removing the PRL by MgCl2 treatment, and reincubating with labeled PRL. In ei...
TL;DR: Results lend support to the concept that cells in the bovine adrenal cortex can obtain cholesterol for steroid hormone synthesis through the receptor-mediated uptake of plasma LDL.
Abstract: Low density lipoprotein (LDL)-binding activity was measured in whole homogenates and membranes prepared from fresh bovine adrenal cortex by an ultracentrifugation assay. The binding site for 125I-labeled LDL in isolated membranes shared the properties of the LDL receptor previously demonstrated in intact monolayers of cultured bovine adrenocortical cells. The amount of high affinity [125I]iodo-LDL-binding activity in the adrenal cortex was 6- to 12-fold higher than in the medulla of the same glands. Large amounts of high affinity [125I]iodo-LDL-binding activity were also present in the ovarian corpus luteum but not in the ovarian interstitium. Lesser amounts of high affinity binding activity were observed in 14 other bovine tissues. These results lend support to the concept that cells in the bovine adrenal cortex can obtain cholesterol for steroid hormone synthesis through the receptor-mediated uptake of plasma LDL.
TL;DR: It is found that low vertebrates, such as frogs and fish, have insulin receptors that by multiple function criteria are very similar to those of birds and mammals, and a sharp pH dependence of binding was observed with both mammalian and nonmammalian receptors.
Abstract: The characteristics of the insulin-receptor interaction have been examined in different species of vertebrates, including mammals (man, rat, mouse, and guinea pig), birds (turkey and chicken), amphibians (frog), and bony fish (trout). We found that low vertebrates, such as frogs and fish, have insulin receptors that by multiple function criteria are very similar to those of birds and mammals. Thus, a sharp pH dependence of binding was observed with both mammalian (optimum, 7.8–8.0) and nonmammalian (optimum, 7.2–7.6) receptors. The effect of temperature on association, dissociation, and steady state binding was also very similar. In general, at higher temperatures (30–37 C) binding was faster than at lower temperature (4 C), but at steady state the level of binding was inversely related to the temperature. Further, in all of the species examined, analysis of equilibrium binding data produced curvilinear Scatchard plots, and unlabeled insulin accelerated the dissociation of labeled insulin compatible with ...
TL;DR: The results suggest an androgen inhibition and an estrogen stimulation of serum AVP levels, which paralleled the presumed changes in serum estradiol.
Abstract: In the present study we have examined the effects of androgens and estrogens on circulating arginine vasopressin (AVP). Adult male Wistar rats had serum AVP levels of 0.4 μU/ml. Two weeks after bilateral castration, AVP rose to 2.6/nU/ml, but daily testosterone administration (100 μg/100 g BW) to the castrate males prevented the AVP increase (0.8 μU/ml). During a normal estrous cycle, adult female Wistar rats had AVP values of 0.6 μU/ml during diestrus, 4.6 μU/ml on the morning of proestrus, 1.3 μU/ml on the afternoon of proestrus, and 1.5 μU/ml on the day of estrus. These changes in AVP paralleled the presumed changes in serum estradiol. Two weeks after bilateral ovariectomy of the adult female rats, AVP was 1.4 μU/ml but daily estradiol injections (100 fig/100 g BW) to the castrate females produced a rise of serum AVP to 5.0 μU/ml. The results suggest an androgen inhibition and an estrogen stimulation of serum AVP levels.
TL;DR: Pineal melatonin in reproductively competent males was found to exhibit a daily rhythm; night values were 10-fold higher than day values; and a difference in the phasing of the pinealmelatonin rhythm relative to the time of day was seen.
Abstract: One purpose of this study was to determine if pineal melatonin is altered by chronic exposure to a lighting schedule which induces gonadal atrophy in the male Syrian hamster. Pineal melatonin in reproductively competent males was found to exhibit a daily rhythm; night values were 10-fold higher than day values. Exposure of males to a lighting cycle with a short photoperiod (10-h light, 14-h dark) caused gonadal atrophy but did not alter either the amplitude of the increase or the duration of the period melatonin was elevated. However, a difference in the phasing of the pineal melatonin rhythm relative to the time of day was seen between these groups. Although lights were turned on at the same time for both groups, pineal melatonin just before this time was basal in the animals exposed to the short photoperiod and maximal in animals exposed to the longer photoperiod (14-h light, 10-h dark). The second purpose of this study was to investigate the acute regulation of pineal melatonin. The nocturnal increase ...