Showing papers on "Prolactin published in 1969"

Radioimmunoassay for rat prolactin.

Abstract: The most commonly used method for measuring prolactin in biological samples has been the pigeon crop bioassay of Lyons (1). It is possible with this method to estimate the prolactin content of pituitary preparations and of other tissues containing relatively high concentrations of this hormone (a minimum of about 0.03 IU or 2 μg of NIH-P-B1, 13 IU/mg); however, it was not possible to assay the prolactin present in serum from normal animals. Recently, double antibody radioimmunoassay techniques have been developed for ovine (2) and bovine prolactin (3) and a radioimmunoassay for rat prolactin (4) which uses a chromatoelectrophoresis step to separate free prolactin-125 I from that bound to the antibody has also been reported. These techniques are sufficiently sensitive to quantitate serum levels of prolactin. This communication describes the development of a double antibody radioimmunoassay for rat prolactin capable of measuring the amount of prolactin in 100 μl of serum from immature female rats or in 25 μ...

Effect of Pregnancy on the Somatotroph and the Prolactin Cell of the Human Adenohypophysis

Abstract: Human anterior pituitary glands from both sexes ranging in age from fetuses through elderly subjects, as well as pregnant and post-partum cases, were studied using a modification of Brookes' stain (Carmoisine L and orange G) that can distinguish 2 types of acidophil cells. The large-granuled, irregularly shaped, “carmoisinophilic” prolactin cell is present in significant numbers only in pregnancy and the postpartum period. There is a concomitant fall in the number of organeophilic somatotrophs in these groups. A few “mixed” cells containing both types of granules were seen. The data did not support or refute the concept that the prolactin cell is derived from the somatotroph. However, an alternative explanation should be considered, namely, that the somatotroph is inhibited by the production of large amounts of chorionic “growth hormone-prolactin” (placental lactogen); this suppression may continue for some time after delivery. The lack of suppression of the prolactin cell by placental lactogen m...

Progesterone withdrawal as the lactogenic trigger in the rat.

Abstract: Lactogenesis, as indicated by the appearance of mammary lactose, follows ovariectomy and/or hysterectomy and the fall in the concentration of progesterone in the plasma preceding normal parturition in the pregnant rat. It is suppressed by administered progesterone in all cases, and by prolactin after hysterectomy. The natural lactogenic signal may occur 30 hr. before parturition, due to conversion of progesterone to 20α-hydroxypregn-4-en-3-one in the ovaries. Changes in the concentration of corticosterone, oestrogen and prolactin in the plasma either do not occur or do not constitute a lactogenic signal.

Influence of Norepinephrine and Catecholamine-Depleting Agents on the Synthesis and Release of Prolactin and Growth Hormone1

Abstract: The in vitro incorporation of leucine- 4,5-3H into rat pituitary glands and its subsequent release into the incubation medium were studied. Quantitation of prolactin and growth hormone was by measurement of intensity of the bands obtained with the polyacrylamide gel technique without bioassay. Most of this newly synthesized prolactin is released into the medium and not retained within the gland. The addition of norepinephrine (10-6M) caused a 70–85% decrease in the amount of radioactive prolactin released by the gland during a 7-hr incubation. An accumulation of labeled prolactin occurred in the treated glands, indicating the primary action of norepinephrine was to decrease prolactin release. The accumulation, however, was not proportional to the degree of inhibition of release, indicating that prolactin synthesis was secondarily inhibited. An increase in the radioactive prolactin in the gland was detectable 30 min afterthe addition of norepinephrine and was statistically significant 30 min later. Similar...

Prolactin-dependent rat mammary cancer: a model for man?

Abstract: Previous studies have induced mammary tumors in rats and investigated the endocrine factors involved in maintaining the growth of these tumors. These studies have indicated that the pituitary plays a role in the estrogenic stimulation of rat mammary tumor growth. To further characterize the pituitary factor rats with DMBA-induced mammary tumors that had regressed after oophorectomy and adrenalectomy were injected with ovine prolactin. Prolactin induced a reactivation of tumor growth and this growth stopped and the tumors regressed promptly when prolactin was discontinued. These findings suggested that the effects of estradiol on mammary tumor growth may be mediated through the effects on pituitary prolactin secretion. Perphenazine a tranquilizer with demonstrated mammotrophic and lactogenic effects was shown to promote tumor growth in these rats and to stimulate the secretion of prolactin. Overall the findings from this animal study suggest that prolactin may be the most significant hormone in maintaining mammary tumor growth. Although this process may also be applicable to human breast cancers prolactin has not yet been isolated as a distinct hormone from human pituitaries. Isolation of human prolactin and the development of an immunoassay for this hormone are encouraged to facilitate the management of human mammary tumors. If prolactin is the decisive endocrine factor in human breast cancer medical control of the secretion of this hormone could have major implications for the prevention as well as management of this disease.

Lactose Synthetase: Progesterone Inhibition of the Induction of α-Lactalbumin

Abstract: Lactose synthesis in the mammary gland is dependent on the hormonally controlled synthesis of the two protein components of lactose synthetase, α-lactalbumin and a galactosyltransferase. Prolactin induces the synthesis of both proteins in mammary gland explants treated with insulin and hydrocortisone, but the induction kinetics cannot account for the asynchronous synthesis of the two proteins that are observed in vivo. Progesterone appears to take part in the control of lactose synthesis and acts to repress the formation of α-lactalbumin throughout pregnancy. At parturition, when the concentration of progesterone in the plasma decreases, the rate of α-lactalbumin synthesis increases.

In Vivo Effect of Sex Hormones on the in Vitro Synthesis of Prolactin and Growth Hormone in Normal and Pituitary Tumor-Bearing Rats

Abstract: The in vivo effects of hormone-secreting pituitary tumors MtTW5, StW5 and 7315a on the in vitro synthesis of prolactin and growth hormone by rat pituitary gland have been studied. The in vitro incorporation of leucine-4,5-3H into these hormones of male and female rats was followed by subjecting homogenates of the pituitary glands and the incubation medium to polyacrylamide gel electrophoresis. Transplantation of 7315a, a prolactin- and ACTH-secreting tumor; MtTW5, a prolactin- and growth hormone-secreting tumor; or StW5, a growth hormone-secreting tumor, into intact female or male rats, caused a decrease in the incorporation of leucine-4,5-3H into prolactin. This decrease in prolactin synthesis was promptly reversed by administration of polyestradiol phosphate to tumor-bearing rats. The labeling of prolactin was also greatly stimulated in intact and castrated nontumor rats by the administration of estrogen and testosterone, while 17α-hydroxyprogesterone caproate injection was without effect. The incorpora...

Regulation of Lipid Metabolism and Progesterone Production in Rat Corpora Lutea and Ovarian Interstitial Elements by Prolactin and Luteinizing Hormone

Abstract: The effects of prolactin in vivo and LH in vitro on synthesis of progesterone and 20α-hydroxypregn-4-en-3-one in isolated, 3-dayold corpora lutea and remaining ovarian elements (interstitial tissue and follicles) of intact rats have been examined. Prolactin (200 μg administered sc twice daily) increased in vitro synthesis of progesterone approximately 4-fold in corpora lutea, and decreased synthesis of 20α-hydroxypregn-4-en-3-one to the same extent; “total progestin” accumulation in vitro was not altered by prolactin treatment. A slight inhibition of synthesis of both steroids in interstitial elements resulted from prolactin treatment. LH (2 μg/ml) added to incubation media significantly increased (by about 50 %) the synthesis of total progestin in corpora lutea only from prolactin-treated rats, the increase being predominantly due to progesterone. Synthesis of both steroids was much lower in interstitial elements than in corpora lutea in the absence of LH; addition of LH caused 7-to 9-fold increases in s...

Differentiation of growth hormone- and prolactin-containing acidophils with peroxidase-labeled antibody.

Abstract: In order to verify the concept that growth hormone and prolactin are contained in two different populations of acidophils, sections of Bouin-fixed rat hypophyses were stained immunochemically. For this purpose the histochemical demonstration of peroxidase was utilized after sequential application to the tissue section of rabbit antiserum to human growth hormone (or antiserum to rat prolactin) followed by application of peroxidase-labeled sheep antiserum to rabbit gamma-globulin. It was found that growth hormone cells and prolactin cells, when revealed immunochemically, corresponded structurally to cell types that could be differentiated with reasonable certainty in sections stained with the Masson trichrome procedure. When delineated immunochemically, growth hormone cells were larger and more densely arranged in the adult male than in the intact female; they exhibited little change in the female after ovariectomy. In contrast, prolactin cells were large and frequent in the female hypophysis but were small and less frequent in the male and in the female after ovariectomy. By double-staining, growth hormone and prolactin cells were differentiated in the same section. It was concluded that (a) growth hormone and prolactin are contained in, and presumably secreted by, two different populations of acidophils; and (b) the Masson procedure permits a reasonably accurate differentiation of the two cell types.

Ultrastructural, histologic and hormonal characterization of a prolactin-rich human pituitary tumor.

Abstract: The pituitary tumor removed from a patient with the Forbes-Albright syndrome was studied by light microscopy, by electron microscopy, and by hormonal analysis. The patient did not have detectable levels of plasma growth hormone following arginine infusion and lacked clinical features of acromegaly. Galactorrhea, present for 3 yr, ceased after hypophysectomy. By light microscopy the tumor was a pituitary adenoma composed of cords of densely granulated eosinophiles with a few chromophobes and basophiles. The eosinophilic granules in the tumor cells differed from growth hormone granules in size, shape and staining characteristics. The tumor granules were more irregular and averaged 500–600 mμ in diameter, in contrast to growth hormone granules which average 350–400 mμ in diameter. The strong erythrosin staining of the tumor granules was not abolished by orange G as it was in growth hormone granules from control cadaver pituitaries. Positive erythrosin staining is a characteristic property shared by ...

Plasma levels of testosterone in male rabbits following copulation.

Abstract: It is well established that the rabbit ovulâtes in response to mating and a marked ovarian release of 20a-hydroxypregnen-4-en-3-one will occur shortly after coitus in this species (Hilliard, Archibald & Sawyer, 1963). This change in progestin secretion following mating corresponds with the increase of gonado¬ trophin in peripheral blood (Hilliard, Hayward & Sawyer, 1964), and the release of interstitial cell stimulating hormone (icsh) and prolactin from the pituitary gland (Desjardins, Kirton & Hafs, 1967). Moreover, Taleisnik, Caligaris & Astrada (1966) noted a decrease in pituitary content of icsh and an increase in plasma icsh in female rats following copulation. The level of ascor¬ bic acid in the ovary of these animals was lower than in control rats. The hormonal response of the male gonad to copulation is less overt and has received little attention. Copulation will increase the blood levels of icsh and decrease the pituitary concentration of the hormone in the male rat (Taleisnik et al., 1966). The secretion of androgenic steroids into the spermatic venous blood of anaesthetized rabbits appears to increase shortly after coitus (Endroczi, 1962) and this increase is not found in male rabbits with hypothalamic lesions. Since testosterone is the major androgen secreted by the male gonad, it was deemed important to study fluctuations of this hormone in the peripheral blood of the rabbit following coitus.

The calcium-mediated promotion of mitotic activity in rat thymocyte populations by growth hormone, neurohormones, parathyroid hormone and prolactin.

Abstract: Growth hormone, oxytocin, parathyroid hormone, prolactin and lysine vasopressin strongly stimulate mitotic activity in rat thymocyte populations maintained in vitro. These hormones have no mitotic effect on cells maintained in calcium-free medium. It is concluded that they stimulate mitosis only indirectly by sensitising the mitotically competent segment of a thymocyte population to the action of calcium. The stimulatory action of calcium itself is opposed by low concentrations of the mucopolysaccharide chondroitin sulphate. However, the inhibitory action of chondroitin sulphate can be overcome by growth hormone. A possible common mechanism of action of these hormones on mitotically competent cells is discussed.

3 - Prolactin (Fish Prolactin or Paralactin) and Growth Hormone

Abstract: In higher vertebrates, prolactin has physiological actions on the biological features that are missing from fishes. Prolactin is considered a causal agent in the induction of maternal behavior and broodiness in mammals and birds, although it is not certain whether this is a direct action or one mediated by gonadal steroids. This chapter discusses the different effects that have been described, following the administration of mammalian prolactin to teleosts. This chapter also explains the growth hormone in fishes. Growth hormone is best known and most readily characterized as the pituitary factor that promotes the overall growth of the body, even when acting in the absence of the other pituitary hormones. All studies are concerned with the physiology of growth hormone (GH) in fishes that relate to the stimulation of body growth, and there is little published data on other aspects of its action.

Hormonal induction and regulation of lactose synthetase in mouse mammary gland.

Abstract: The augmentation of lactose synthetase activity during late pregnancy and lactation was measured by using both a tissue-culture assay and a cell-free assay The results indicated at least a 100-fold augmentation in specific activity between late pregnancy and lactation The cell-free assay indicated that the activities of both subunits of this enzyme had increased to 20–30% of the value during lactation by the last day of pregnancy The tissue-culture assay, however, showed activities only 3–4% of the maximum at the time of parturition This suggests that not all the enzyme present in the tissue before lactation commenced was active Since at all stages of pregnancy and lactation the B subunit, α-lactalbumin (which is also a milk protein), was rate-limiting, it is suggested that the rate of lactose synthesis may be linked to the rate of milk-protein synthesis Both subunits of lactose synthetase could be induced in tissue culture by the hormones insulin+hydrocortisone+prolactin Of the three hormones, prolactin appeared to be the `trigger' that induced the synthesis of these proteins if the tissue had been stimulated previously by insulin+hydrocortisone

The fine structural localization of acid phosphatase in the prolactin cell of the teleost pituitary following the stimulation and inhibition of secretory activity

Abstract: Fine structural studies have been made upon the prolactin cells of Poecilia latipinna when the fish is subjected to a series of changes in its environmental salinity. Under the regimen employed it is shown that the secretory mechanism of the cell is initially stimulated in fresh water and then inhibited in salt water. The latter event is accompanied by the appearance of demonstrable acid phosphatase activity within the Golgi complex and by the formation of a variety of acid phosphatase-positive bodies. The way in which this acid hydrolase activity is concerned with the removal of surplus secretory granules is described and discussed.

Effect of prolactin on the tadpole tail fin. I. Stimulatory effect of prolactin on the collagen synthesis of the tadpole tail fin.

Abstract: Bovine prolactin stimulated the growth of connective tissues both in the tail fins and in other regions of the tadpole tail. Correlated with the morphological effect of the hormone on the tadpole tails, protein synthesis in tail fins was promoted about 2 times by prolactin. Experiments performed to determine the kind of protein, the synthesis of which was stimulated by prolactin, revealed that the hormone specifically enhanced collagen synthesis about 40 folds as compared to untreated animals.

Prolactin in the postpartum rat: synthesis and release in the absence of suckling stimulation.

Abstract: Postpartum female rats deprived of suckling stimulation while being kept continuously with pups nonetheless suspended ovarian cyclicity for an average of 16 days and responded to uterine trauma by forming deciduomata. These results show that the extramammary stimulation afforded by young is alone capable of sustaining prolactin output from the adenohypophysis of the postpartum rat.

Immunohistochemical Localization of ACTH and Prolactin in the Pituitary Gland of Adult Migratory Sockeye Salmon (Oncorhynchus nerka)

Abstract: Antibodies to porcine adrenocorticotrophic hormone (ACTH), Synacthen (synthetic corticotrophin, Ciba), and ovine prolactin were prepared in rabbits and the antisera were tested for specificity against several pituitary hormones. The gamma-globulin fractions of the antisera were conjugated with fluorescein isothiocyanate and the labelled antibodies were "purified" by column chromatography.Fresh-frozen sections of pituitary glands of adult migratory sockeye salmon were incubated with the antibody solutions and examined with a fluorescence microscope. The resulting antigen–antibody complex could be localized by re-photographing the same or alternate sections after fixation and staining. Anti-ACTH and anti-Synacthen appeared to be bound specifically by the epsilon cells, whereas anti-prolactin reacted with the eta cells of the rostral pars distalis. Pituitary glands collected at various stations along the migratory route, including one seawater sample, showed the same reactivity. Other glands were prepared fo...