Showing papers in "Endocrinology in 1973"

Bovine Parathyroid Hormone: Minimum Chain Length of Synthetic Peptide Required for Biological Activity

Abstract: Several fragments representing progressively shorter segments of the amino terminal region of bovine parathyroid hormone have been prepared by solid-phase peptide synthesis and bioassayed in the in vitro rat kidney adenyl cyclase assay and the in vivo chick hypercalcemia assay. These studies have denned the minimum chain length required for activity. The synthetic amino terminal 1-34 peptide was highly potent (80% on a molar basis of the natural hormone in vitro and 130% in vivo). It was found that deletion of the amino terminal residue (alanine) resulted in a marked decrease in activity and removal of the second residue (valine) at the amino terminus completely abolished activity in both assay systems. Greater shortening was tolerated at the carboxyl terminus. Peptide 1-27 was still active in the in vitro assay; deletion of residue 27 led to loss of biological activity in both assays. (Endocrinology 93: 1349, 1973)

Serum luteinizing hormone, prolactin and progesterone levels during pregnancy in the rat.

Abstract: Serum levels of luteinizing hormone (LH) and prolactin were measured twice daily, and those of progesterone once daily, throughout gestation in rats with confirmed pregnancies, and in which parturition was seen to have occurred on day 23. Serum LH concentration during the first 11 days of pregnancy was distinctly higher than during the period between days 13–19, with a conspicuous pivot—point occurring at about day 12; beginning on day 20 and continuing to term, a progressive increase occurred, which was not contiguous with the acute, post—partum, ovulation inducing surge of LH. Serum prolactin level did not show as distinct a pattern of change, although highly erratic levels during the initial 10 days, and consistently low levels during most of the second half of pregnancy were noted. When related to the pattern of changes in the levels of serum LH and prolactin, the changes in serum progesterone level were seen to be inversely related to those in serum LH during the period from day 11 to term (r = -0.97...

Fluctuations in Plasma Testosterone Levels in Adult Male Rats and Mice

Abstract: Testosterone (T) levels in the plasma of male laboratory rats and mice were measured by radioimmunoassay. There was a striking individual variation with values ranging from less than 1 ng/ml to over 30 ng/ml in mice of the same age and strain housed under identical conditions. Using chronic indwelling catheters inserted into a jugular vein, blood was collected from adult conscious male rats every 24 hr for 4 or 8 days and every 30 min for 2l/2 or 8 hr. Considerable differences in plasma T levels were observed between different animals, and 2– to 5–fold fluctuations of T concentrations in the plasma were detected between samples collected from the same animal at different times. These large and irregular changes in plasma levels of T are unlike the fairly stable levels observed in the human but bear certain resemblance to the pulsatile release of T described in bulls and rams and perhaps also to the social dominance related differences in plasma T levels in Rhesus monkeys. (Endocrinology 92: 1223, 1973)

Studies on the mechanism of estrogen biosynthesis. 8. The development of inhibitors of the enzyme system in human placenta.

Abstract: Structural features of over 100 steroids and some non—steroids were evaluated systematically as inhibitors of estrogen biosynthesis in human placental microsomes. The microsomes were preincubated with and without potential inhibitors, and then were incubated with [4–14C] androst–4–ene–3,17–dione or [4–14C]3P—hydroxyandrost— S—en—17–one (DHA) and an NADPH generating system. After adding tritiated estrogens as recovery markers, the estrogens were isolated by thin—layer chromatography and were assayed using dual—label scintillation counting to determine percent conversion and inhibition produced. C10 A4–3–keto compounds were better inhibitors than the corresponding ring A reduced (5

Positive and negative feedback control by estrogen of luteinizing hormone secretion in the rhesus monkey.

Abstract: Silastic capsules containing 17β–estradiol were implanted subcutaneously into rhesus monkeys ovariectomized 3–18 months earlier. These capsules released the steroid at a rate which resulted in plasma estrogen concentrations (70 pg/ml) approximating those observed during the early follicular phase of the normal menstrual cycle. These estrogen levels were maintained for as long as the implants were kept in place (1 yr and 9 months). Following the implantation of estradiol, the elevated plasma LH concentrations characteristic of untreated ovariectomized monkeys declined to the low levels associated with the early follicular phase of the cycle and remained there for the duration of the study. The administration of a single subcutaneous injection of estradiol benzoate to these chronically suppressed ovariectomized animals elicited a discharge of LH resembling the spontaneous, preovulatory LH surge. These findings support the conclusion that the positive feedback action of estradiol, which initiates the LH surg...

Corticosteroid Feedback Control of ACTH Secretion: Effect of Stress-Induced Corticosterone Secretion on Subsequent Stress Responses in the Rat1

Abstract: The stresses of electrical shock or laparotomy were repeated at various intervals up to 24 hr after the initial stress in an attempt to demonstrate inhibition of the second response as a consequence of corticosterone secreted after the first stress. In all cases the second response was equal to or greater in magnitude than the first. When the stress of prolonged (60-90 min) restraint was paired with the minor stress of injection several hr later, no inhibition of the corticosterone response to injection was observed. However, if the plasma corticosterone levels provoked by restraint stress were mimicked by injections of corticosterone or of ACTH, the subsequent response to injection stress was inhibited. We conclude from these, and previous studies in the adrenalectomized rat, that corticosterone does act to inhibit ACTH secretion, but that stress causes a prolonged period of hyper—responsiveness in either CNS or anterior pituitary components of the adrenocortical system. (Endocrinology 92: 1367, 1973)

The roles of plasma binding and receptor specificity in the mineralocorticoid action of aldosterone.

Abstract: The current hypothesis of the mechanism of action of aldosterone includes an initiating step of binding of the steroid to stereospecific receptor proteins in target tissues. In view of the very low circulating levels of aldosterone relative to other adrenal steroids, there must exist potent specificity—conferring mechanisms to insure appropriate aldosterone occupancy of mineralocorticoid receptors. Two specificity—conferring mechanisms are described which are posited to allow aldosterone occupancy of its appropriate receptor.In vitro, renal aldosterone binding sites are shown to fall into two classes. Those with a higher affinity for aldosterone—Kdlss (37 C)≅ 5X10-10—are termed Type I; those with a lower affinity—Kdiss (37 C)≅ 2.5 X lO-8— Type II. Desoxycorticosterone (DOC) has ∼80% the affinity of aldosterone for both sites. Corticosterone (B) has a high affinity for Type II sites, but less than 2% of the affinity of aldosterone for Type I. From the relative affinities of the three steroids for Type I, t...

Tihe Concentrations of Progesterone, Estrone and Estradiol-17β in the Plasma of Pregnant Rabbits

Abstract: The concentrations of progesterone (P), estrone (E1) and estradiol-17β (E2β) in the peripheral plasma of rabbits during the course of pregnancy have been determined by radioimmunoassay. The mean concentration of P increased from 5.3 ng/ml on day 3 to 17-19 ng/ml on days 12-15 and declined slowly thereafter until term. The mean concentration of E1 remained between 20-35 pg/ml throughout gestation. The levels of E2β showed fluctuations with peaks on day 6 (83 pg/ml), day 15 (59 pg/ml) and day 30 (48 pg/ml). The concentrations of P and E2β rose and fell similarly between day 9 and day 24. Thereafter, E2β rose but P declined. The ratio, P/E2β, fell sharply from 480 to 140 between days 27 and 30. (Endocrinology 93: 971, 1973)

A high-affinity androgen-binding protein (ABP) in rat testis: evidence for secretion into efferent duct fluid and absorption by epididymis.

Abstract: An androgen-binding protein (ABP) was detected in 105,000 × g supernatants of rat testis homogenates after removal of endogenous steroids by charcoal extraction. The ABP was identical to that previously demonstrated in highspeed supernatants of epididymis homogenates. When the exocrine secretion of the testis was blocked by ligation of efferent ducts, ABP increased in testis supernatant in proportion to the retention of testicular fluid while at the same time it disappeared from epididymis supernatant, first from the caput and later from the cauda. Treatment with large doses of testosterone did not alter the disappearance from epididymis. ABP disappeared almost completely from caput supernatant within three days after efferent duct ligation. When efferent ducts and corpus epididymidis were ligated simultaneously to block the flow of luminal fluid into and out of the caput, the disappearance of ABP from caput supernatant was only partially prevented. This finding suggested that a major portion of ABP is ei...

Effect of LH on steroidogenesis and cyclic AMP accumulation in rat Leydig cell preparations and mouse tumor Leydig cells.

Abstract: The effect of LH and FSH on mouse tumor Leydig cells as well as Leydig cell preparations obtained from rat testes by digestion with collagenase were investigated. LH but not FSH increased the cyclic AMP content of both cell preparations. The amounts of LH required to stimulate cyclic AMP synthesis maximally were at least an order of magnitude greater than that required for maximal stimulation of steroidogenesis. LH failed to stimulate cyclic AMP synthesis in tubule preparations. A simple dilution procedure was sufficient to terminate the stimulatory effect of LH on cyclic AMP synthesis in Leydig cells, whereas the same procedure failed to affect the steroidogenic response to LH. (Endocrinology 93: 127, 1973)

Serum Prolactin During Various Physiological States and Its Relationship to Milk Production in the Bovine

Abstract: Serum prolactin was measured in 55 cows 2–4 hr before, immediately after and 1 hr after milking for the duration of lactation or week 44, whichever occurred first. Serum prolactin increased in response to stimuli associated with milking, but this response was largest at 8 weeks; of lactation (77 ng/ml) and then gradually decreased as lactation advanced until at 32 weeks prolactin was no longer released. As prolactin concentrations increased in the pre—milking serum samples the amount subsequently released by the milking stimulus was reduced (p < 0.01). The correlation between serum prolactin measured 2 to 4 hr before milking and milk yield was very low (r = -0.03), although similar calculations for samples collected immediately after and 1 hour after milking (r = 0.36 and 0.18, respectively) were significant (p < 0.01). Within—stageof— lactation correlations between serum prolactin and milk yield were very low and sometimes negative during early lactation, but after 12 to 24 weeks of lactation the correla...

Effect of hypophysectomy, castration and androgen replacement upon the fertilizing ability of rat epididymal spermatozoa.

Abstract: It has been demonstrated that in the rat, spermatozoa become able to fertilize ova when they reach the proximal region of the cauda epididymidis Epididymal spermatozoa lose this ability 3 days after castration and 4 days after hypophysectomy Ligation of the ductuli efferentes or sham hypophysectomy has no effect Testosterone propionate (2 mg/kg/day) prevents the effect of castration or hypophysectomy Cyproterone acetate (20 mg/kg/day) successfully inhibits the effect of exogenous testosterone (2 mg/ kg/day) Spermatozoa from the distal cauda epididymidis lose their fertilizing ability within 4 days after castration (9%) and 6 days after hypophysectomy (13%) Testosterone propionate (2 mg/kg/day) maintains the fertilizing ability of the spermatozoa from the distal cauda Procedures (castration or hypophysectomy) which cause a decline in circulating androgen levels, hasten sperm transit through the epididymis Castration interferes with the acquisition by the spermatozoa of their mature progressive patt

Induced LH surges in the rhesus monkey: Strength-duration characteristics of the estrogen stimulus

Abstract: The strength—duration characteristics of the increments in circulating estrogen required to elicit LH surges in the rhesus monkey were investigated by implanting (sc) Silastic capsules containing estradiol—17β for varying periods of time during the early follicular phase of the menstrual cycle. The magnitude of the resultant “square—wave” increments in serum estrogen concentration was varied by the number of capsules implanted. It was found that serum estrogen concentrations below 100 pg/ml were ineffective in eliciting LH surges, even when applied for as long as 120 hr. Serum estrogen concentrations of 100– 200 pg/ml had! to be maintained for approximately 42 hr to induce LH discharges, whereas 200–400 pg/ml were effective when applied for 36 hr. Supraphysiological estrogen levels of 1200 to 2000 pg/ml elicited LH surges when sustained for only 24 hr. In all instances, LH surges were initiated before the capsules were removed, showing that this response is not a consequence of estrogen withdrawal. The re...

Production of antiserum to LH-releasing hormone (LH-RH) associated with gonadal atrophy in rabbits: development of radioimmunoassays for LH-RH.

Abstract: Repeated injections of synthetic LH-RH decapeptide, adsorbed on polyvinylpyrrolidone and emulsified with complete Freund's adjuvant, resulted in the production of a specific antiserum to LH-RH in 2 of 3 rabbits. The animals which produced this antiserum showed a reduction of pituitary LH content and marked atrophy of the testes. The antiserum-antibody complex was detected by the complement fixation test. The antiserum was capable of binding 125I labeled LH-RH. After iodination of LH-RH (using 125I and either the chloramine T or lactoperoxidase method) separation of the iodination products on CMC yielded 3 main peaks of radioactivity: The first was free iodide, the second was labeled peptide with low immunoreactivity, and the third was immunoreactive peptide. This 3rd peak consisted of 2 or 3 subpeaks; the leading subpeak(s) were more readily bound by antiserum than the trailing one(s). Binding of these fractions to antiserum was increased in the presence of small amounts of unlabeled LH-RH (a phenomenon c...

Glucocorticoid Receptors in Rat Kidney: The Rinding of Tritiated-Dexamethasone1

Abstract: The effects of glucocorticoid hormones are thought to be initiated by binding to stereospecific intracellular receptor proteins in target tissues. The kidney enjoys a variety of functions influenced by glucocorticoid hormones. High affinity glucocorticoid receptors have been demonstrated in adrenalectomized rat kidney by the specific binding of dexamethasone (DM). These receptors have been designated Type II, and can be distinguished from high affinity mineralocorticoid receptors (Type I) and the CBGlike corticosterone receptors (Type III) on the basis of differing affinities for a series of physiological and synthetic steroids. By Scatchard plot analysis, the equilibrium (dissociation) constant of the 3HDM–cytoplasmic receptor complex was 5 X 10-9M (25 C), and the concentration of binding sites 1.6 X 10-13 moles per mg protein in the cytoplasmic high speed supernatant (HSS). Similar concentrations of receptor were found in outer cortex and medulla—papilla. The affinity of the Type—II receptor for steroid...

Effects of Serotonin Precursors and Melatonin on Serum Prolactin Release in Rats

Abstract: A single intravenous injection of tryptophane, 5-hydroxytryptophane, serotonin or melatonin was given to rats on the morning of proestrus and to hypophysectomized, pituitarygrafted female rats. The 5-hydroxytryptophane increased serum prolactin about 9 fold by 30 min after injection and about 6 fold by 1 hr after injection as compared to control values; it also doubled serum prolactin values in hypophysectomized rats with an anterior pituitary graft. Tryptophane approximately doubled serum prolactin over control values by 30 min and 2 hr after injection, but these differences were not significant statistically. Serotonin itself did not significantly alter serum prolactin levels, but melatonin significantly increased serum prolactin over control levels by 1 and 2 hr after injection. These results suggest that brain serotonin, its precursors and melatonin may have a role in stimulating prolactin release, and thereby serve to counter the inhibitory effects of hypothalamic catecholamines on prolactin release....

Characteristics of Gonadotropin Receptors of Porcine Granulosa Cells during Follicle Maturation1

Abstract: In order to determine why granulosa cells obtained from large preovulatory porcine follicles luteinize spontaneously in culture, whereas cells obtained from adjacent less mature small follicles fail to luteinize spontaneously, or in the presence of exogenous gonadotropin, gonadotropin receptors in granulosa cells obtained from increasingly mature small, medium and large porcine follicles have been studied. Granulosa cells obtained from small, medium and large follicles did not differ significantly in size. Granulosa cells obtained from small (1–2 mm), medium (3– 5 mm) and large porcine follicles were incubated with 125I—hCG. Granulosa cells obtained from large follicles bound 10–lOOO–fold more 125I—hCG (623,300 ± 44,890 cpm/5 X 106 cells; n = 12) compared to small follicles of the same ovary or from other ovaries (7,554 ± 1,983 cpm/5 X 106 cells; n = 16). Medium follicle cells bound only a slightly greater amount of hCG than small follicle cells. Qualitatively the binding of small, medium and large follic...

Pineal Control of a Seasonal Reproductive Rhythm in Male Golden Hamsters Exposed to Natural Daylight and Temperature

Abstract: When intact adult male golden hamsters are exposed to natural photoperiodic and temperature conditions during the winter months, their reproductive organs degenerate and plasma levels of LH decrease significantly. Pinealectomized hamsters kept under identical conditions do not experience the winter decline in reproductive activity. As spring approaches, the gonads of the non—pinealectomized hamsters regenerate to a functionally mature state. If hamsters with intact pineal glands are placed in near continuous darkness beginning in May (after having experienced reproductive atrophy in the previous winter), their reproductive systems do not regress. These results indicate that the neuroendocrine— gonadal axis may normally be refractory to pineal secretory products during the summer months or the pineal gland may be physiologically “exhausted” after a period of activity. The findings show that: (a) the photoperiod normally controls the seasonal reproductive rhythm in this species, and (b) the effects are medi...

Autoradiographic localization of radioactivity in the rat brain after the injection of 1,2-3H-testosterone.

Abstract: The localization of radioactivity in the brain of immature intact and mature castrated Sprague—Dawley rats was investigated by drymount autoradiography at 1 hr after the injection of l,2–3H-testosterone. Radioactivity is found to be selectively concentrated and retained in specific neurons in the nucleus (n.) arcuatus and the n. ventromedialis hypothalami, the n. preopticus medialis, the n. interstitialis striae terminalis, the n. septi lateralis, the hippocampus and the amygdala. The topographic distribution of androgenconcentrating neurons agrees well with areas in the brain that have been associated with the regulation of gonadotropin secretion and male sex behavior. The autoradiographic data are consistent with the hypothesis that androgen feedback occurs at hypothalamic and extrahypothalamic sites in the central nervous system. (Endocrinology 92: 251, 1973)

Sex Steroid Influence on Hepatic Gluconeogenesis and Glycogen Formation1

Abstract: Hepatic gluconeogenesis and glycogen formation were studied in female rats following 21 days of parenterally administered sex steroids to assess the effects of these hormones on liver carbohydrate metabolism and their role in the development of insulin antagonism during pregnancy. Estradiol, progesterone or the two hormones in combination were administered in sesame oil, and control rats received oil alone. Daily dosages of estradiol and progesterone did not exceed 5 μg or 5 mg, respectively. 128 Animals were subdivided into 2–hr and 24–hr fasted groups. Percentage conversion of intravenous alanine— U–14C or pyruvate–3–14C into glucose–14C was followed over a 30 min interval. Suppression of this conversion was most consistently produced with the combined regimen in association with increased percentages of precursor radioactivity appearing in hepatic glycogen. Plasma insulin concentrations were significantly increased in all sex steroidtreated animals relative to control values as was the liver glycogen c...

Periovulatory time courses of circulating gonadotropic and ovarian hormones in the rhesus monkey.

Abstract: Samples of peripheral blood were taken from 4 intact rhesus monkeys every 3 hr for a 72–hr period encompassing the midcycle LH surge, and assayed for LH, FSH, estradiol, estrone and progesterone. The LH and FSH peaks were essentially parallel. They were continuous, symmetrical, and monophasic, with a mean duration of approximately 50 hr. The rate of decrease in LH concentration during the descending phase of the surge did not approach the half-life of LH in the monkey, indicating that secretion was continuing during this time. A sharp rise in estradiol accompanied the initial increase in LH, resulting in a peak which preceded that of LH by 9–15 hr. Progesterone was undetectable in peripheral plasma until 15 hr after LH began to rise, reaching a small peak within 6 hr of the LH peak. Estradiol started to decrease before the decrease in progesterone, but both steroids reached nadirs approximately 24 hr after the LH peak. In a separate group of 12 animals, the earliest evidence of ovulation was obtained appr...

Lordosis reflex intensity in rats in relation to the estrous cycle, ovariectomy, estrogen administration and mating behavior.

Abstract: Lordosis in response to manual palpation of the flanks and perineum was markedly facilitated by simultaneously probing the vaginal cervix. While palpation without cervical probing never induced lordosis in 96 ovariectomized, hormone-untreated rats, addition of cervical probing induced lordosis in 48% of these individuals. Cervical probing alone never induced lordosis. Estrogen administration (as little as a single injection of 1.0 μg/100 g body wt) significantly increased the intensity (extent of dorsiflexion, measured photographically), and probability of occurrence, of lordosis in response to palpation with cervical probing. Lordosis in response to mounting attempts by males, or by palpation alone, occurred only rarely at estrogen dosages lower than 10.0 μg/100 g body wt. Lordosis intensity and probability of occurrence varied significantly in relation to the estrous cycle; they were higher in proestrus and the transitional periods of diestrus-proestrus and proestrus-estrus, than in estrus, metestrus or...

Two Phases of Adipose Tissue Metabolism in Pregnancy: Maternal Adaptations for Fetal Growth1

Abstract: Maternal hyperphagia and hyperinsulinism characterize the second half of rat gestation. Within this period two distinct metabolic phases have been identified. Initially (day 12), fat storage is enhanced with a 2–fold greater conversion of glucose into adipose tissue triglyceride fatty acids and a diminished release of free fatty acids. Placental and fetal fuel needs are minimal at this stage. After day 12 until term, insulin effectiveness progressively deteriorates, adipose tissue fatty acid formation from glucose declines to 1/3 of control, and maternal fat stores are increasingly mobilized as free fatty acids. These events are closely synchronized with the growth of the feto—placental unit. These results indicate that maternal fat storage is promoted by increases in food intake and plasma insulin at mid—term. Despite continuation of hyperphagia and hyperinsulinism into late gestation, maternal fat storage declines because of diminished tissue responsiveness to insulin. This mechanism is viewed as an ada...

The EflFects of Gonadal Steroids on Plasma Gonadotropins and Prolactin in the Rat1

Abstract: The effects of single sc injections of various doses of estradiol benzoate (Eb) and testosterone propionate (Tp) on plasma levels of LH, FSH and prolactin have been reinvestigated in castrate rats of both sexes. Our results indicate that Eb or Tp inhibited release of LH in castrate rats of both sexes. Males were more sensitive to the inhibitor effect of the low dose of Tp than females. The steroids also lowered plasma FSH levels in spayed females; however, in castrated males Eb stimulated FSH release and a decrease in FSH followed the injection of only the highest dose (2 mg) of Tp. Eb and Tp had a synergistic effect in inhibiting FSH release in the male. Both steroids stimulated release of prolactin in castrate males and females (no sex difference in release of prolactin in response to Eb was observed; however, males appeared more sensitive to Tp treatment). Single injections of progesterone (P) in spayed females produced variable results. High doses inhibited LH release and elevated prolactin levels. Ef...

Thyrotropin releasing hormone (TRH): neurotransmitter regulation of secretion by mouse hypothalamic tissue in vitro

Abstract: The regulation of thyrotropinreleasing hormone (TRH) secretion by putative neurotransmitters was studied in vitro by measuring the release of radioactive TRH from mouse hypothalamic fragments which had been pulselabelled with tritiated TRH precursor amino acids. Both dopamine and norepinephrine, when added to the incubation media in a concentration of 10-4M or 1O-5M, increased the release of 3H TRH. The TRH stimulatory effects of dopamine, but not of norepinephrine were abolished by Disulfiram, a β-oxidase inhibitor, thus suggesting that dopamine was effective after conversion to norepinephrine. Release of 3H-TRH was decreased upon addition of serotonin at 10-4M. Acetylcholine in the presence of either Eserine or the acetylcholine analogue, carbachol, had no effect on TRH release. These findings suggest that the regulation of TRH release is under a dual monoaminergic control system with a positive noradrenergic and a negative serotoninergic component. (Endocrinology 93: 626, 1973)

Changes in Serum Prolactin and Gonadotropins During Sexual Development of the Male Rat

Abstract: Serum levels of FSH, LH and prolactin were determined during development in male rats. Blood was collected from the trunk after decapitation. Prolactin levels were very low at 15 and 20 days of age, underwent an initial rise at 25 days, and then remained relatively constant until 50 days. A secondary increase occurred thereafter to reach maximal adult values at 90 days. Serum FSH was readily detectable at 15 and 20 days, rose to a peak at 25 and 30 days and then declined back to the original levels by 60 days. It remained relatively constant thereafter. On the other hand, serum LH levels underwent a very gradual increase from 15 days to reach a maximum at 70 days which was similar to levels found in adults. Initiation of the rapid phase of testicular growth at 25 days could be correlated with the elevations of serum FSH and prolactin levels. Rapid growth of sex accessories began somewhat later in the presence of continued relatively high prolactin levels and falling levels of FSH. Later growth of the sex ...

Nuclear receptor-estrogen complex: relationship between concentration and early uterotrophic responses.

Abstract: The quantitative relationship between the amount of receptor—estrogen complex in the nuclear fraction of rat uterine cells and the extent of early uterotropic responses was studied in the immature rat. The quantity of nuclear receptor—estrogen complex, R—E, is maximal 1 hr after estradiol treatment. A decrease in nuclear R—E between 1 and 6 hr following estradiol treatment was observed which was dependent on hormonal dosage. During this 5–hr period, 70–80% of the sites were lost from the nuclear fraction following pharmacologic doses (1.0–2.5 μg) while a 7–9% decrease was observed with physiological doses (0.05–0.1 μg). Maximal increases in uterine weight were obtained when levels of nuclear R—E represented only a fraction of the total quantity of receptor in the uterus. However, a high correlation was observed between water imbibition and the quantity of nuclear R—E present at 3 and 6 hr after estradiol injection. In addition, positive correlations were found between the quantity of nuclear R—E and the e...

Enrichment of Cell Types from the Rat Adenohypophysis by Sedimentation at Unit Gravity

Abstract: The application of a unit gravity cell separation procedure to rat adenohypophysial tissue is described. The results demonstrate (a) that adenohypophysial cells retain their characteristic tinctorial properties after dissociation and sedimentation, (b) that a 2–3–fold enrichment of different cell types can be achieved and (c) that the incorporation rate of labeled amino acids into the protein of dissociated versus non—dissociated adenohypophysial cells is similar. Sedimentation of cells from tissues of thyroidectomized or lactating animals yielded enriched populations of thyrotrophs and lactotrophs respectively. This cell separation technique offers a novel approach to the isolation, purification, and study of the pituitary cell types.(Endocrinology 92: 265,1973)

Radioimmunoassay of Testosterone During Fetal Development of the Rhesus Monkey

Abstract: A radioimmunoassay was developed for measuring testosterone (T) in the plasma of the rhesus monkey (Macaca mulatto). The method is sensitive and specific and can distinguish 20 pg of T when added to plasma from the adrenalectomized- ovariectomized monkey. When plasma obtained from cord blood at various times during gestation was analyzed by this method, the levels of T in plasma from the umbilical artery of males were significantly higher than those in females. Plasma from females did, however, contain small amounts of this hormone with little variation between animals. Large fluctuations in the concentrations of T in plasma from the fetal male were observed. Significantly higher amounts of T were found in the umbilical artery than in the vein in male but not in female fetuses. Castration of the fetus on day 100 of gestation abolished the sex difference in the amounts of T found on day ISO to 156 of gestation. These data indicate that the fetal testis of the monkey is the source of the elevated levels of ...

Evidence for a New Class of Corticosterone Receptors in the Rat Kidney1

Abstract: Recent studies have documented the properties of high affinity renal cytoplasmic receptors for aldosterone (Type I ), and for glucocorticoids (Type II) which bind dexamethasone with about twice the affinity shown for corticosterone. We now present evidence for the existence of a third class of renal cytoplasmic receptors (Type III) which resemble but are probably distinct from plasma corticosteroid—binding globulin (CBG). The Type III sites have a high affinity for corticosterone, Kdisg = 3 X 10–9M at 25 C, and very low affinities for both aldosterone and dexamethasone. The Type III receptors follow saturation kinetics in the binding of 3H—corticosterone, and the relative affinities of various steroids for these sites is in the following sequence: corticosterone > cortisol > deoxycorticosterone > progesterone > aldosterone > dexamethasone. Within the kidney, the inner medullapapilla showed substantially higher concentrations of Type III receptors than the outer cortex. The protein nature of the type III r...