Showing papers on "Prolactin published in 1970"
TL;DR: Rat serum prolactin as determined by radioimmunoassay during the estrous cycle was found to be highest during estrus (68.5 ±7.4 ng/ml) and lowest in diestrus (27.6 ± 5.0 ng/ML), and there were no cyclic changes in serum prolACTin levels in mature male rats.
Abstract: Rat serum prolactin as determined by radioimmunoassay during the estrous cycle was found to be highest during estrus (68.5 ±7.4 ng/ml) and lowest in diestrus (27.6 ± 5.0 ng/ml). Serum prolactin levels during proestrus, estrus and metestrus were not significantly different. There were no cyclic changes in serum prolactin levels in mature male rats. Estrogen injections increased both pituitary and serum prolactin, whereas ovariectomy decreased both. During the first 3 days of pregnancy, serum prolactin was higher (19.1 ±7.4 to 30.2 ±4.5 ng/ml) than during the following 18 days (8.3 ± 1.1 to 10.9 ±1.2 ng/ml). On the 22nd day of pregnancy serum prolactin levels rose to 29.2 ±13.8 ng/ml. On the 1st day post partum, serum prolactin increased to 65.5 ±19.0 ng/ml, and a high serum concentration was maintained by the suckling stimulus for at least 8 days. On the 15th and 23rd days post partum, serum prolactin fell to about half (25.7 ±5.5 ng/ml) of the level on the first day post partum. Removal of litters from mo...
382 citations
TL;DR: It is concluded that multifunctional rat pituitary cells in culture show unusual promise for further studies of the control of expression of organ-specific activities in mammalian cells.
Abstract: Several established clonal strains of rat pituitary cells which produce growth hormone in culture have been shown to secrete a second protein hormone, prolactin. Prolactin was measured immunologically in culture medium and within cells by complement fixation. Rates of prolactin production varied from 6.6 to 12 µg/mg cell protein per 24 hr in four different cell strains. In these cultures ratios of production of prolactin to growth hormone varied from 1.0 to 4.1. A fifth clonal strain produced growth hormone but no detectable prolactin. Intracellular prolactin was equivalent to the amount secreted into medium in a period of about 1–2 hr. Both cycloheximide and puromycin suppressed prolactin production by at least 94%. Hydrocortisone (3 x 10-6 M), which stimulated the production of growth hormone 4- to 8-fold in most of the cell strains, reduced the rate of prolactin production to less than 25% of that in control cultures. Conversely, addition of simple acid extracts of several tissues, including hypothalamus, to the medium of all strains increased the rate of production of prolactin six to nine times and decreased growth hormone production by about 50%. We conclude that multifunctional rat pituitary cells in culture show unusual promise for further studies of the control of expression of organ-specific activities in mammalian cells.
326 citations
TL;DR: It is indicated that low doses of estrogen are more effective than high doses for increasing AP and serum prolactin levels, and no evidence that large doses of estroge...
Abstract: Serum and anterior pituitary (AP) prolactin levels from mature ovariectomized rats were assayed after injection with daily doses of 0.1–500 ng estradiol benzoate (EB) or 0.5–10 mg progesterone for 6 days. Doses of 0.1, 1 or 5 μg EB increased serum prolactin concentration 2-, 3- and 10-fold, respectively, over ovariectomized controls, and doses of 10–500 μg EB evoked smaller increases in serum and AP prolactin levels. AP prolactin concentration and content were increased 3- to 4-fold. Doses of 0.5, 1 or 4 mg progesterone partially inhibited the increase in serum prolactin levels evoked by 1 μg EB, but only the inhibition by 4 mg progesterone was significant. A daily dose of 4 mg progesterone injected alone appeared to have no effect on serum and AP prolactin levels, but a 10 mg dose significantly increased prolactin secretion. These results indicate that low doses of estrogen are more effective than high doses for increasing AP and serum prolactin levels, and provide no evidence that large doses of estroge...
294 citations
TL;DR: Of the 10 experimental animals, each, without exception, showed full maternal behavior at between 35 and 40 hr, which represents a significant reduction in latency from the average of 6–7 days characteristic of untreated nulliparae, but represents as well a uniformity in time of onset closely approaching that exhibited by the puerperal female.
236 citations
TL;DR: Compared to decapitation, laparotomy and bleeding under ether anesthesia induced 3- to 8-fold increases in serum prolactin values at all times studied dur-ing the estrous cycle except on the afternoon of proestrus, when no further increase in already elevated levels was observed.
Abstract: The effect of method of blood col-lection on serum prolactin and LH levels was determined throughout the estrous cycle of the rat. Five animals were decapitated and 5 were bled from the abdominal aorta following lap-arotomy under ether anesthesia at each of the following times during the estrous cycle: 3 PM on diestrus days 1, 2 and 3 and 10 AM and 3 PM on the days of proestrus and estrus. Compared to decapitation, laparotomy and bleeding under ether anesthesia induced 3- to 8-fold increases in serum prolactin values at all times studied dur-ing the estrous cycle except on the afternoon of proestrus, when no further increase in already elevated levels was observed. Ether-laparotomy also elevated prolactin titers in ovariectomized females but not in males. Prolactin levels on the morning of proestrus in animals anesthetized with ether and then decapitated were higher than in decapitated animals but less than in ether-laparotomized animals. Serum concentrations of LH were not affected by any of the procedur...
236 citations
TL;DR: Rat adenohypophyses were incubated in medium 199 containing l-14C-glycine or a Krebs-Ringer-bicarbonate solution with glucose and a mixture of essential and non-essential amino acids and catecholamines decreased total radioactive glycine incorporated into medium and pituitary prolactin but after 4 hr of incubation this decrease was not statistically significant.
Abstract: Rat adenohypophyses were incubated in medium 199 containing l-14C-glycine or a Krebs-Ringer-bicarbonate solution with glucose and a mixture of essential and non-essential amino acids. Dialyzed medium and anterior pituitary homogenates were elect rophoresed on polyacrylamide gel. After staining with Amido Black, the growth hormone and prolactin bands were quantified by microdensitometry and cut from the gel column for measurement of radioactivity. Growth hormone and prolactin contained in the medium were also measured by radioimmunoassay techniques. Epinephrine and norepinephrine inhibited prolactin release into the medium and this was associated with a proportionate rise in anterior pituitary prolactin. The catecholamines decreased total radioactive glycine incorporated into medium and pituitary prolactin but after 4 hr of incubation this decrease was not statistically significant. Inhibition of prolactin release occurred with concentrations of .5 μg/ml or greater of norepinephrine, and 1 μg/ml or greater...
184 citations
TL;DR: Some of the hormone-mediated processes that occur during development of the mouse mammary gland in vitro are discussed, which provide opportunities for chemical dissection that facilitate analysis of sequential events occurring during development.
Abstract: Publisher Summary Multiple hormone dependencies provide the investigator with opportunities for chemical dissection that facilitate analysis of sequential events occurring during development. This, in turn, aids the delineation of the action of individual hormones. This chapter discusses some of the hormone-mediated processes that occur during development of the mouse mammary gland in vitro. During the first three postnatal weeks, the cells in the epithelial cord undergo little, if any, proliferation. In the course of the next month or two, presumably under the influence of larger amounts of estrogen and progesterone during puberty, the epithelial cells multiply so as to form ducts and primitive alveoli along the connective tissue septa. With the attainment of sexual maturity at the age of 2–3 months, mammary epithelial-cell proliferation virtually ceases. During pregnancy and the early postpartum period, epithelial growth resumes so that the lactating gland contains ducts and alveoli in profusion. Functional and cytological innovations also take place at this time. Within a few weeks after the end of lactation, the gland reassumes the histological and functional profile characteristic of the tissue in the mature nonpregnant animal. The cycle is repeated with the onset of another pregnancy. In all the studies described in the chapter, an organ-culture method was used. Expiants were supported on siliconized lens paper that floated on Medium 199 containing penicillin and various combinations of crystalline beef insulin, hydrocortisone, and ovine prolactin.
153 citations
TL;DR: The in vitro influence of dopamine on the in vitro incorporation of leucine-4,5-3H into rat pituitary gland prolactin and growth hormone was studied and catecholamine primarily inhibited.
Abstract: The in vitro influence of dopamine on the in vitro incorporation of leucine-4,5-3H into rat pituitary gland prolactin and growth hormone was studied. This catecholamine primarily inhibited
143 citations
13 Jan 1970
TL;DR: Radioimmunoassay of all 3 hormones indicated that the increases in serum LH and prolactin did not necessarily occur simultaneously, and may have been elevated due to anesthesia and exsanguination and showed a rapid increase which occurred simultaneously with elevated LH and FSH on the afternoon of proestrus.
Abstract: A detailed analysis was made of circulating luteinizing hormone (LH) follicle-stimulating hormone (FSH) and prolactin throughout the estrous cycle in rats. Vaginal cytology was recorded daily for 18 or 23 days in 2 groups of adult female rats 300 and 400 per group. The presence of distended uteri or tubal ova was noted at the time of exsanguination under ether anesthesia. Serum concentrations of LH FSH and prolactin were determined by radioimmunoassay. In 404 rats with regular 5-day cycles all 3 hormones reached maximum concentrations on the afternoon of functional proestrus. During the next 3 days FSH decreased progressively and LH levels indicated a diurnal fluctuation with minimum concentrations during darkness. Serum prolactin may have b een elevated due to anesthesia and exsanguination and showed a rapid increase which occurred simultaneously with elevated LH and FSH on the afternoon of proestrus. Radioimmunoassay of all 3 hormones indicated that the increases in serum LH and prolactin did not necessarily occur simultaneously. Hypophysectomy and sequential heart puncture of proestrus rats during maximum hormone release showed disappearance rates (half-lives) for LH FSH and prolactin of 20 110 and 13 minutes respectively.(AUTHORS MODIFIED)
133 citations
TL;DR: Evidence has been presented to show that LH maintains pregnancy up to day 12 by stimulating steroidogenesis.
Abstract: Administration of specific and wellcharacterized rabbit antisera to ovine luteinizing hormone (LH) to pregnant rats, before day 12 of gestation, resulted in vaginal bleeding followed by resorption of fetuses. This effect of the antiserum could not be reversed by the administration of either ovine prolactin or extracts of day 12 rat placentae. Homotransplantation of 2 pituitaries under the kidney capsule also did not reverse this effect. Whereas 0.25–5 μg estradiol-17β was ineffective, 4 mg of progesterone could overcome the effects of the antiserum. Deprivation of LH even for 2–8 hr was injurious to fetal growth. These effects of the antiserum could be reversed by the simultaneous administration of LH. Thus, evidence has been presented to show that LH maintains pregnancy up to day 12 by stimulating steroidogenesis. Of the 3 gonadotropins (LH, prolactin and FSH) tried, administration of LH during the second half of pregnancy resulted in postponement of parturition. Similar results were obtained with the ad...
128 citations
TL;DR: The effects of insulin, hydrocortisone, and prolactin on the morphology of explants from midpregnant mouse mammary glands were studied and there is excellent correlation between the ultrastructural appearance of the alveoli and their capacity to synthesize casein.
Abstract: The effects of insulin, hydrocortisone, and prolactin on the morphology of explants from midpregnant mouse mammary glands were studied. Insulin promotes the formation of daughter cells within the alveolar epithelium which are ultrastructurally indistinguishable from the parent cells. The addition of hydrocortisone to the medium containing insulin brings the daughter cells to a new, intermediate level of ultrastructural development by effecting an extensive increase of the rough endoplasmic reticulum (RER) throughout the cytoplasm and an increase in the lateral paranuclear Golgi apparatus. When prolactin is added to the insulin-hydrocortisone medium, the daughter cells complete their ultrastructural differentiation. There is a translocation of the RER, Golgi apparatus, and nucleus and the appearance of secretory protein granules within the cytoplasm. There is excellent correlation between the ultrastructural appearance of the alveoli and their capacity to synthesize casein.
TL;DR: Maetz and his associates have shown that a primary osmoregulatory function of prolactin is the reduction of extrarenal sodium outflux which is uncontrolled, or poorly controlled, after removal of the hypophysis.
Abstract: THE discovery, in 1959, that prolactin enables hypophysectomized killifish (Fundulus heteroclitus) to live in fresh water1,2 stimulated much investigation of the osmoregulatory functions of this hormone in euryhaline teleosts3. The presence of prolactin, or its teleostean equivalent (paralactin), is necessary for fresh water survival in many euryhaline cyprinodonts and in some unrelated species. In others, such as the eel (Anguilla anguilla), prolactin participates less in electrolyte homeostasis, and hypophysectomized fish of such species can withstand fresh water. Maetz and his associates4–6 have shown that a primary osmoregulatory function of prolactin is the reduction of extrarenal sodium outflux which is uncontrolled, or poorly controlled, after removal of the hypophysis. This becomes critical when a prolactin-dependent species, such as F. heteroclitus, is transferred to fresh water.
TL;DR: The results indicate that removal of hypothalamic inhibition of prolactin release by pituitary transplantation or by appropriate lesion placement in the hypothalamus results in elevated serum Prolactin levels.
Abstract: Serum prolactin levels were determined by radioimmunoassay in hypophysectomized, ovariectomized rats bearing 0, 1, 2, or 4 anterior pituitaries (AP) underneath the kidney capsule at 1, 2, 4, 6, 8, and 10 weeks after transplantation. Rats with no AP transplants had barely detectable levels of serum prolactin, whereas rats with 1 AP transplant from female cycling rats had serum prolactin values as high as those seen in estrous rats (120 ng/ml serum). In rats bearing 2 AP transplants, serum prolactin increased to 170 ng/ml serum, whereas 4 AP transplants elevated serum prolactin to 250 ng/ml, which is about equivalent to that in lactating postpartum rats (280 ng/ml). Injections of estradiol benzoate (1 µg/day for 5 days) into rats bearing 0, 1, 2, or 4 AP transplants, beginning 10 weeks after transplantation, increased serum prolactin over pre-treatment levels, except in the rats with no pituitary transplants. Bilateral lesions placed in the median eminence or anterior hypothalamus of ovariectomized rats significantly increased serum prolactin to 125 and 85 ng/ml, respectively, as compared with sham-lesioned controls (20 ng/ml). Posterior hypothalamic lesions increased serum prolactin concentration slightly and lesions in the amygdaloid nuclei had no effect. These results indicate that removal of hypothalamic inhibition of prolactin release by pituitary transplantation or by appropriate lesion placement in the hypothalamus results in elevated serum prolactin levels.
TL;DR: A highly sensitive bioassay has been developed for prolactin, which uses a mammalian end organ and which is capable of measuring the hormone in unextracted human plasma.
Abstract: A highly sensitive bioassay has been developed for prolactin, which uses a mammalian end organ and which is capable of measuring the hormone in unextracted human plasma. High prolactin activity, largely neutralizable with antiserum to human growth hormone, is stimulated along with high immunoassayable growth hormone by insulin-induced hypoglycemia. High prolactin activity, not neutralizable with antiserum to growth hormone, exists with low concentrations of plasma growth hormone in postpartum patients and patients with galactorrhea.
TL;DR: Data indicate that the increase in endogenous cyclic AMP brought about by luteinizing hormone is due to a stimulation of the adenyl cyclase rather than to an inhibition of the phosphodiesterase.
TL;DR: Addition of theophylline to pituitary gland, incubated in vitro, increased both the synthesis and release of growth hormone, and although fluoride greatly stimulated growth hormone release, it completely inhibited the incorporation of leucine into the hormone.
Abstract: Effects of prostaglandins on the incorporation of [4,5-3H]leucine into growth hormone and its subsequent release into the incubation medium were studied. Incubation of rat anterior pituitary glands with 10-6 M prostaglandin PGE1 in tissue culture medium 199 for 7 hr caused a 40-300% increase in the release of labeled growth hormone into the incubation medium. PGE1 at 10-8 M increased growth hormone synthesis but not release. At 10-6 M, PGE2 had effects similar to PGE1; PGA1 increased growth hormone synthesis but not release. PGF2α was without effect on either synthesis or release of growth hormone.
Prolactin synthesis and release were not affected by prostaglandins. All of the prostaglandins, at 10-4 M, increased adenyl cyclase activity in the pituitary gland but phosphodiesterase activity was unaltered. Dibutyryl cyclic AMP, with or without caffeine, caused an up to 300% increase in labeled growth hormone release. No consistent effect of prolactin was observed. If potassium concentration was increased 10-fold, a 215% increase in growth hormone release was observed. A combination of hypertonic potassium and 10-6 M PGE1 increased growth hormone release 325%, suggesting that potassium and prostaglandins act by independent mechanisms. Addition of theophylline to pituitary gland, incubated in vitro, increased both the synthesis and release of growth hormone. Although fluoride greatly stimulated growth hormone release, it completely inhibited the incorporation of leucine into the hormone. Similarly, puromycin inhibited synthesis of growth hormone but did not block release induced by prostaglandin, dibutyryl cyclic AMP, theophylline, or fluoride. Prostaglandins increase pituitary adenyl cyclase activity and, presumably via cyclic AMP, increase growth hormone release, independently of protein synthesis.
TL;DR: It was concluded that increased electrophoretic heterogeneity of the hormones, in the absence of proteinases, can be attributed to a nonenzymic deamidation.
TL;DR: A single intraperitoneal injection of reserpine, chlorpromazine, C, alphamethyl- para-tyrosine and AMPT in proestrous rats produced profound elevations in serum prolactin 30 min to 4 hr after injection, which indicates that these 4 drugs evoked rapid release of Prolactin from the pituitary, and that AMMT also elicited rapid synthesis of prolACTin.
Abstract: A single intraperitoneal injection of reserpine (R), chlorpromazine (C), alphamethyl- para-tyrosine (AMPT) or alpha-methylmeta-tyrosine (AMMT) in proestrous rats produced profound elevations in serum prolactin 30 min to 4 hr after injection. R, C and AMPT decreased pituitary prolactin concentration, whereas AMMT increased it. This indicates that these 4 drugs evoked rapid release of prolactin from the pituitary, and that AMMT also elicited rapid synthesis of prolactin. The increased release of pituitary prolactin may be related to inhibition by the drugs of catecholamine activity in the hypothalamus and/or to reduced hypothalamic PIF content. A single intraperitoneal injection of dopamine (D), epinephrine (E), norepinephrine (NE) or serotonin (S) had no significant effect on serum prolactin levels 1 or 2 hr after injection. D, E and NE also had no effect on serum prolactin values when injected intracarotidly. The higher doses of E and D but not NE produced a small decrease in pituitary prolactin concentra...
TL;DR: The results indicate that increases in nuclear biosynthetic activity can be initiated by the interaction of these hormones with the superficial membrane structures of mammary cells.
TL;DR: In KRP prolactin synthesis and release was greatly decreased compared to that found using KRB, whereas growth hormone synthesis andRelease proceeded equally well in either buffer, and similar but less dramatic effects were found using Ca++-free KRP buffer.
Abstract: The incorporation of leucine-4,5-3H into growth hormone and prolactin by rat anterior pituitary glands incubated in buffers of Krebs-Ringer-bicarbonate (KRB), Krebs-Ringerphosphate (KRP) and tissue culture Medium 199 was measured. In KRP prolactin synthesis and release was greatly decreased compared to that found using KRB, whereas growth hormone synthesis and release proceeded equally well in either buffer. Addition of HCO3− to KRP buffer increased greatly the release and synthesis of prolactin. When potassium was omitted from the buffers, a decrease in incorporation of radioactive leucine into prolactin and growth hormone was observed. The absence of Ca++ from KRB greatly diminished prolactin synthesis and decreased release, and similar but less dramatic effects were found using Ca++-free KRP buffer. Growth hormone synthesis and release was decreased by incubation in Ca++-free KRB, but when the calcium was omitted from KRP buffer, a decrease in the release of growth hormone was not accompanied by a decr...
TL;DR: An enzyme in extracts of luteinized rat ovaries was found which catalyzed the synthesis of cholesterol esters from palmitic acid-l-14C and cholesterol and required ATP, Mg++ and Coenzyme A for expression of activity.
Abstract: An enzyme in extracts of luteinized rat ovaries was found which catalyzed the synthesis of cholesterol esters from palmitic acid-l-14C and cholesterol and required ATP, Mg++ and Coenzyme A for expression of activity. This enzyme, sterol acyl transferase, was associated predominantly with the 100,000 ×g pellet fraction obtained from 10,000 ×g supernatant fractions of homogenized ovaries. The enzyme which hydrolyzes cholesterol esters, sterol esterase, was assayed simultaneously in 100,000 ×g supernatant fractions. Transferase and esterase levels were both markedly reduced (p <.01) when assayed 3 days after hypophysectomy (90 and 70%, respectively). Administration of rat prolactin (2 IU; sc; b.i.d.) was completely effective in preventing the decline of both enzymes after hypophysectomy, whereas LH (NIH-LH-S14; 50 μg daily in sesame oil+5% beeswax) was without effect. In hypophysectomized animals, LH and prolactin combined were less effective in maintaining transferase activity than prolactin treatment alone...
TL;DR: It was concluded that estrogen acts directly on the hypophysis, the spread of the effects reflecting the direction of blood flow within the gland, and support the hypothesis that the pituitary gland serves as a site for feedback action by estrogen.
Abstract: The direct action of 17 β-estradiol and cholesterol on cells of the pituitary pars distalis, as revealed by staining with peroxidase-labeled antibody, was studied in female rats. Pellets of pure cholesterol and of estradiol mixed with cholesterol were implanted into the left lobe of the pars distalis 14–32 days after ovariectomy and left in place for 7–16 days. Rabbit antisera to rat prolactin, human growth hormone, human chorionic gonadotropin (for gonadotropes — presumably luteinizing hormone cells), and porcine corticotropin were used. In no case were cells altered in the contralateral lobe of the pars distalis; cholesterol likewise had no significant effect on the ipsilateral lobe. However, in the ipsilateral lobe containing an estrogen pellet, prolactin cells were hypertrophied and hyperplastic; cells assumed to be responsible for luteinizing hormone secretion were reduced in size and stained more intensely; and growth hormone cells were reduced in size. Corticotropin cells remained unaffected. For the most part estrogenic effects were distributed ventrally, caudally and laterally from the pellet and not far medially, never reaching the midline. It was concluded that estrogen acts directly on the hypophysis, the spread of the effects reflecting the direction of blood flow within the gland. These observations support the hypothesis that the pituitary gland serves as a site for feedback action by estrogen.
TL;DR: The administration of 2.5 mg prolactin twice daily for 10 days, beginning 20 days after adreno‐ovariectomy, raised the number and size of regressed mammary tumors to the pre‐operative levels, while the half dose of Prolactin had no effects.
Abstract: The effects of exogenous administration of bovine prolactin and bovine growth hormone (GH) on 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary tumor were investigated in female Sprague-Dawley rats. Rats were bilaterally adrenoovariectomized 15 days after the appearance of the first palpable mammary tumors and were treated with either prolactin or GH beginning the next morning. Marked stimulation of incidence and growth of mammary tumor and of normal mammary gland growth followed subcutaneous injections of 1.25 or 2.5 mg prolactin twice daily for 20 days. GH had no effects on mammary tumor, whereas it accelerated the growth of normal mammary gland and increased the body weight. The administration of 2.5 mg prolactin twice daily for 10 days, beginning 20 days after adreno-ovariectomy, raised the number and size of regressed mammary tumors to the pre-operative levels, while the half dose of prolactin had no effects.
These results indicate that prolactin is the principal hormone responsible for the growth of DMBA-induced mammary tumor of the rat, whereas GH has only a minimal role in the growth of the tumor.
TL;DR: Human pituitary glands were incubated with 3H-l,4,5-leucine in Krebs-Ringer bicarbonate buffer to study the biosynthesis and secretion of human pituitsary proteins generally and growth hormone specifically.
Abstract: Human pituitary glands were incubated with 3H-l,4,5-leucine in Krebs-Ringer bicarbonate buffer to study the biosynthesis and secretion of human pituitary proteins generally and growth hormone specifically. After 4 and 24 hr, anti-HGH serum precipitated only 3 and 13%, respectively, of the 3H-proteins in the medium. Following gel filtration of the medium on Sephadex, a single radioactive protein peak emerged with an elution volume which was not quite coincident with the elution volume of HGH and the protein peak. FSH, LH and TSH were present in earlier fractions and ACTH in later fractions. The total amount of all 4 hormones in the media was a thousandfold less than the amount of HGH in the media. Anti-HGH serum precipitated less than 5% of the 3H-proteins in the tubes which contained HGH, yet the latter accounted for more than 80% of the proteins in these fractions. Hence, the specific activity of the remaining proteins present in these fractions was very much greater than that of HGH. In the tis...
TL;DR: Explants of rat adenohypophyses were incubated in medium 199, Earle's saline, or modified Earle’s saline (K‐Earle's) with different calcium, magnesium, sodium and potassium concentrations for 4‐6 hr at 37° C in 5% CO2 in O2.
Abstract: 1. Explants of rat adenohypophyses were incubated in medium 199, Earle's saline, or modified Earle's saline (K-Earle's) with different calcium, magnesium, sodium and potassium concentrations for 4-6 hr at 37 degrees C in 5% CO(2) in O(2).2. The amount of prolactin and growth hormone in explants and in medium was estimated by disk electrophoresis and densitometry.3. Low calcium inhibited prolactin secretion by 40-60%. Low magnesium and slightly increased (5x) magnesium (4.1 mM) did not influence prolactin secretion in either 1.8 mM or low calcium, but 10 and 20 mM magnesium inhibited secretion by 50 and 70%, respectively. Inhibition of prolactin secretion by high magnesium was reversible.4. Decreasing sodium by 80% had no effect on prolactin secretion, but low sodium inhibited the sustained, although not acute, secretion of this hormone.5. Low potassium did not affect the secretion of either prolactin or growth hormone. Increased potassium (32 or 54 mM) slightly stimulated prolactin secretion by adenohypophyses of males but had no effect on the secretion of this hormone by female glands.6. In 1.8 mM calcium, growth hormone secretion by pituitaries of males and females was markedly stimulated by increased potassium, but it was not appreciably affected by high potasium in low calcium. Increased potassium did not stimulate growth hormone secretion in medium containing low sodium with normal calcium.7. Secretion of prolactin and growth hormone by rat adenohypophyses is dependent upon calcium, but only growth hormone secretion is markedly stimulated by increased potassium. The difference in responsiveness to increased potassium, between the somatotrophs and lactotrophs, may be related to the predominant mode of hypothalamic control of these hormones.
TL;DR: It is concluded that prolactin is a hormone which can be released by various stimuli and that milking is the most powerful of the stimuli for the acute prolactIn discharge from the anterior pituitary gland in the cow as well as in the goat at least in the early stage of lactation.
Abstract: Plasma prolactin concentration of serial blood samples taken from cows and goats bearing indwelling jugular venous catheter was assayed by a radioimmunologic procedure. Using 9 lactating cows, the response of prolactin release to milking was investigated at different stages of lactation. In all cases, plasma prolactin levels rapidly increased and reached a peak 4-20 min after the start of milking. The magnitude of the response was considerably different with the stage of lactation in the same cow. The peak of plasma prolactin released by milking was highest in the early stage of lactation (189±34ng/ml, SE), and decreased thereafter with the advance of lactation. Conspicuous response of prolactin release with a 40-to 100-told increase by milking was also obtained in the lactating goats. Feeding could induce a rapid elevation of plasma prolactin in the lactating cow. Mimic-or sham-milking in heifers and in virgin goats in which teats were pulled and the udder was massaged by hands for 5 min, induced an acute prolactin release within 2 min after the start of stimulation, although there was no milk flow. Stressful stimulus associated with venipuncture also elevated the plasma prolactin in the lactating and non-lactating animals. These findings lead to the conclusion that prolactin is a hormone which can be released by various stimuli and that milking is the most powerful of the stimuli for the acute prolactin discharge from the anterior pituitary gland in the cow as well as in the goat at least in the early stage of lactation. At the same time, a variety of non-specific stimuli can also cause a rapid rise in plasma prolactin concentration.
TL;DR: The in vitro effects of epinephrine, norepinephrine and dopamine on prolactin release by the rat pituitary were studied and indicate that the effects of catecholamines on pituitaries prolact in vitro are dose dependent.
Abstract: The in vitro effects of epinephrine, norepinephrine and dopamine on prolactin release by the rat pituitary were studied in a 4-hr incubation system. The addition of 10 or 20 ng of epinephrine or norepinephrine to 1 ml of a physiological medium containing ½ male rat pituitary significantly increased prolactin release, whereas doses of 200–1000 ng markedly inhibited prolactin release. Incorporation of 2–40 ng of dopamine into the medium had no effect, whereas 80–640 ng significantly decreased prolactin release. These results indicate that the effects of catecholamines on pituitary prolactin release in vitro are dose dependent. (Endocrinology 87: 673, 1970)
Journal Article•
TL;DR: The results indicate that an additional source of prolactin significantly enhances mammary tumorigenesis in the female rat.
Abstract: The purpose of this study was to evaluate the role of pituitary homografts on mammary tumorigenesis in the female Sprague-Dawley rat. Five pituitaries were grafted unilaterally over the inguinal, abdominal, and thoracic regions of the mammary gland and two pituitaries were grafted underneath the kidney capsule of each rat. Pituitaries were obtained from donor rats of varying ages but of the same sex and strain as the recipients. The pituitaries were transplanted to mammary tumor-free 2-month-old nulliparous rats (Group I), 8-month-old nulliparous rats (Group II), and 8-month-old multiparous rats (Group III). Mammary tumor-free nongrafted rats of comparable age and breeding status served as controls for each group. Number and percentage of rats with mammary tumors 9 months after pituitary grafting were: Group I, 13/45 (30%); Group II, 9/12 (75%); and Group III, 8/13 (61%); this contrasted with 2/27 (7%), 1/12 (8%), and 3/16 (19%) in the nongrafted controls. Since pituitary homografts secrete relatively large amounts of prolactin and small amounts of all other pituitary hormones, the present results indicate that an additional source of prolactin significantly enhances mammary tumorigenesis in the female rat.