Effect of estrogen administration on the induction of the plasma prolactin afternoon surge and on anterior pituitary prolactin concentration extracted at different pHs

Ovariectomized (OVX) rats were injected with various doses of polyestradiol phosphate (PEP); the anterior pituitary (AP) prolactin (PRL) concentration and the plasma afternoon surge of PRL were observed 1 week later by radioimmunoassay. AP PRL was extracted using carbonate and phosphate buffers at either pH 7.6 or 10.6. The AP concentration of PRL was greater when the AP was extracted with buffers at pH 10.6 and the phosphate buffer was the most efficient. The concentration of PRL in the AP more closely reflected the magnitude of the estrogen-induced afternoon surge when the AP was extracted at pH 10.6 and this was especially so when the higher levels of estrogen were administered.     

Influence of somatostatin on serum prolactin concentrations of cows during rest and milking

Administration of somatostatin (SRIF) to lactating cows significantly increased basal, premilking serum concentrations of prolactin (PRL), and potentiated PRL release in response to milking and significantly reduced resting concentrations of growth hormone (GH).     

Effects of prolactin (PRL) on gonadotropin release in mice with congenital PRL deficiency

Summary In prolactin (PRL)-deficient male dwarf mice, treatment with PRL stimulates the release of FSH without affecting plasma LH levels. We now report that this effect of PRL is not mediated by the testes and that PRL does not modify FSH or LH release in female dwarf mice.This work was supported by the National Institute of Child Health and Human Development through a grand HD12642 and RIA Core of grant HD10202. We thank NIAMDD and Drs G.D. Niswender and L.E. Reichert, Jr, for reagents used in radioimmunoassays.     

Comparison of intradermal pigeon crop-sac bioassay and double antibody radioimmunoassay for rat prolactin

Summary On an absolute basis, the intradermal pigeon crop-sac bioassay (PCA) gave results that were 20.5% higher than the radioimmunoassay (RIA) in rat anterior pituitary (AP) preparations. A highly significant correlation (r=0.87) was obtained between RIA (in g) and PCA (in Reece-Turner units) when 58 medium samples obtained by culturing rat APs in vitro were assayed for prolactin (PRL) content.Supported by the Charles and Johanna Busch Memorial Fund and by Hatch Amended Funds, Rutgers University-The State University of New Jersey, New Brunswick, NJ 08903, USA.The authors acknowledge the generous supply of rat PRL reference preparation and iodination material for the RIA by NIAMDD, NIH.     

Influence of somatostatin on serum prolactin concentrations of cows during rest and milking

Summary Administration of somatostatin (SRIF) to lactating cows significantly increased basal, premilking serum concentrations of prolactin (PRL), and potentiated PRL release in response to milking and significantly reduced resting concentrations of growth hormone (GH).The author wishes to thank Ayerst Laboratories of Canada for donating the somatostatin for these studies.     

Modification of membrane cholesterol content affects electrical properties and prolactin release of cultured pituitary cells

Summary Treatment of cloned pituitary cells (GH3/B6) with cholesterol-enriched liposomes, which presumably increases membrane cholesterol content, affects the passive and active electrophysiological properties and stimulates the release of prolactin (PRL).Supported by grants from CNRS (ERA 493, ATP Endocrinologie). We thank NIAMDD for providing the reagents for PRL assay.     

Radioimmunoassay of some hormones simultaneously measured in serum and breast cyst fluid

Blood and breast cyst fluid were drawn simultaneously for hormonal determination. There was no difference between serum and cyst fluid values of PRL and TSH. A significant difference was noted for LH (p less than 0.01) and FSH (p less than 0.05), serum concentrations being higher than cyst fluid concentrations.     

Prolactin and growth hormone releasing activity of [D-Met2, Pro5]-enkephalinamide in the rat after systemic administration

Summary The growth hormone (GH) and prolactin releasing (PRL) activity of [D-Met², Pro⁵]-enkephalinamide (EKNH₂), an opioid peptide analog with higher opiate agonist activity that morphine, was compared in the unanesthetized male rat to those of equimolar doses of morphine upon systemic injection. EKNH₂ proved to be a higher PRL, but not GH, releaser than the opiate alkaloid.     

Effect of apomorphine hydrochloride administration on serum concentrations of prolactin,and growth hormone in cattle

Summary Administration of apomorphine hydrochloride to cattle significantly depressed serum prolactin (PRL) concentrations and elevated serum growth hormone (GH) concentrations in a dosimetric fashion.     

Prolactin and growth hormone signal transduction in lymphohaemopoietic cells

The peptide hormones, prolactin (PRL) and growth hormone (GH), are known to regulate numerous target tissues. Among such targets are cells of the immune system, including T cells, B cells, macrophages and natural killer cells. We have cloned a panel of PRL- and GH-inducible T cell genes for use in studies to understand how these hormones through the expression of these genes modulate the biology of immune function cells. This article focuses on the signalling pathways emanating from the PRL receptor (PRL-R) and GH receptor (GH-R), and the expression of PRL-inducible target genes.     

Radioimmunoassay of some hormones simultaneously measured in serum and breast cyst fluid

Summary Blood and breast cyst fluid were drawn simultaneously for hormonal determination. There was no difference between serum and cyst fluid values of PRL and TSH. A significant difference was noted for LH (p<0.01) and FSH (p<0.05), serum concentrations being higher than cyst fluid concentrations.The authors are indebted to Miss J. Meister, E. Dullaert and J. Beck for their skillful technical help. We are also indebted to the National Institutes of Health, NIAMDD and the World Health Organization, International Laboratory for Biological Standards.     

Modifications of membrane cholesterol content affects electrical properties and prolactin release of cultured pituitary cells

Treatment of cloned pituitary cells (GH3/B6) with cholesterol-enriched liposomes, which presumably increases membrane cholesterol content, affects the passive and active electrophysiological properties and stimulates the release of prolactin (PRL).     

Plurihormonality in the secretory granules of the normal human pituitary. An immunoelectron microscopic study

Normal human autopsy anterior pituitary tissue from 5 cases was embedded in LR White resin and immunolabelled using silver-enhanced 5-nm protein A gold probes. Follicle stimulating hormone (FSH), thyroid stimulating hormone (TSH), luteinizing hormone (LH), adrenocorticotrophic hormone (ACTH), growth hormone (GH) and prolactin (PRL) were immunolocalised to the level of secretory granule. A two-sided double-labelling method was used to cross-react two hormones at a time with respect to their corresponding antibodies. All possible combinations of the six pituitary hormones were tested. Plurihormonal granules were found that contained LH + FSH, LH + TSH, and FSH + TSH. Each hormone was also found in monohormonal granules. Granule diameter was significantly larger in the pluri as opposed to monohormonal granules.     

Plurihormonality in the secretory granules of the normal human pituitary. An immunoelectron microscopic study

Summary Normal human autopsy anterior pituitary tissue from 5 cases was embedded in LR White resin and immunolabelled using silver-enhanced 5-nm protein A gold probes. Follicle stimulating hormone (FSH), thyroid stimulating hormone (TSH), luteinizing hormone (LH), adrenocorticotrophic hormone (ACTH), growth hormone (GH) and prolactin (PRL) were immunolocalised to the level of secretory granule.A two-sided double-labelling method was used to cross-react two hormones at a time with respect to their corresponding antibodies. All possible combinations of the six pituitary hormones were tested. Plurihormonal granules were found that contained LH+FSH, LH+TSH, and FSH+TSH. Each hormone was also found in monohormonal granules. Granule diameter was significantly larger in the pluri as opposed to monohormonal granules.     

Somatic growth in hypophysectomized pituitary-homografted rats is promoted by prolactin

Summary Hypophysectomized male rats bearing a homograft of two adenopituitaries under the kidney capsule showed a significant increase in b.wt as compared to hypophysectomized non-homografted animals. Radiommunoassay of growth hormone (GH), ACTH, -MSH,-endorphin and prolactin (PRL) revealed that only the latter was highly increased in the plasma of hypophysectomized homografted rats. These animals showed also increased levels of plasma corticosterone. However, daily injection of corticosterone failed to promote somatic growth in hypophysectomized non-homografted rats. These results suggest that PRL, and not other hormonal factors, promotes somatic growth in hypophysectomized homografted rats, and stress the concept that only PRL is secreted in significant amounts by pituitary homografts.     

Prolactin, growth hormone and the immune system in humans

Prolactin (PRL) and growth hormone (GH) qualify as lymphoid growth and differentiation factors. Yet, long-standing hyper- or hyposecretion of PRL or GH does not induce any significant alteration of the immune system. Subclinical changes in laboratory parameters (such as chemotaxis or phagocytosis by granulocytes or macrophages or natural killer cell activity) have been reported in some of these conditions. The GH-insulin-like growth factor (IGF)-I axis is dysregulated in ageing, in catabolic states and in critical illness. Immune parameters, such as infection rate, are being monitored during clinical trials with GH or IGF-I. Hyperprolactinaemia may play an aggravating role in systemic lupus erythematosus, in autoimmune thyroiditis and in other autoimmune diseases. The patient may benefit from increased alertness about interactions between the endocrine and immune systems.     

The adenohypophysial hormone content of the rat pars tuberalis

Summary The pars tuberalis of the hypophysis was shown to contain LH, which increases after castration, TSH and a very low amount of PRL. FSH was found after castration.This investigation was supported by the Fundación Instituto de Neurobiología and CONICET. The authors want to thank Dr A.F. Parlow for supplying the NIAMDD radioimmunoassay kits.     

Reduced tuberoinfundibular dopaminergic neuronal function in rats after long-term withdrawal of estrogen treatment

Summary Hypothalamic fragments from female rats treated repeatedly with estradiol valerate (EV) and bearing prolactin (PRL)-secreting tumors contained, seven months after the last EV injection, lower concentrations of dopamine (DA) than age-matched controls. Depolarizing concentrations of K⁺ (35 mM) and amphetamine (50 M) evoked in PRL-secreting tumor bearing rats an endogenous DA release significantly lower than in controls.