An immunohistochemical and ultrastructural comparison of the effects of 2-bromo-α-ergocryptine on intrasellar and transplanted rat pituitaries

Summary Following 2 weeks of administration of 2-bromo--ergocryptine, a marked decrease was observed in prolactin immunoreactivity of the grafted pituitaries, whereas no reduction was noted in the intrasellar pituitaries. No evidence of crinophagy was revealed by electron microscopy in prolactin cells of 2-bromo--ergocryptine-treated rats.Acknowledgments. This work was supported in part by the Medical Research Council of Canada (grant MA-6349). The excellent technical assistance of Mrs Cynthia Edwards and secretarial help of Mrs Wanda Wlodarski are gratefully acknowledged.     

Increase in pituitary melanocyte-stimulating hormone activity of genetically obese (ob/ob) mice

Summary Melanocyte-stimulating hormone (MSH) activity was measured in the pituitaries of genetically obese and lean control mice using the frog skin bioassay. Obese mice pituitaries demonstrated very significantly elevated levels of biologically active MSH when compared to their lean littermates. These results support the hypothesis that the elevated levels of pituitary hormones found in obese mice possess true biological activity.     

Inhibition of TSH-stimulated thyroid hormone release and potentiation of TRH-stimulated TSH release by indomethacin in perifusion systems of rat thyroids and pituitaries

Using indomethacin (Ind), a prostaglandin synthesis inhibitor, in vivo experiments in rats and in vitro experiments with perifusion systems of rat thyroids and pituitaries were conducted. After 35 days of intragastric infusion of Ind, serum TSH levels were markedly increased, the thyroid was swollen and, as a consequence, T3 and T4 levels were normal. The T3 release from perifused rat thyroids under continuous stimulation with 10 mU/ml TSH was inhibited significantly (p less than 0.01) by 1.0 X 10(-6) M Ind. On the other hand, the TSH release from perifused rat pituitaries under TRH stimulation was enhanced conspicuously by Ind. It was concluded that Ind decelerated thyroid hormone release from the thyroid and accelerated TSH release from the pituitary in perifusion systems.     

Inhibition of TSH-stimulated thyroid hormone release and potentiation of TRH-stimulated TSH release by indomethacin in perifusion systems of rat thyroids and pituitaries

Summary Using indomethacin (Ind), a prostaglandin, synthesis inhibitor, in vivo experiments in rats and in vitro experiments with perifusion systems of rat thyroids and pituitaries were conducted. After 35 days of intragastric infusion of Ind, serum TSH levels were markedly increased, the thyroid was swollen and, as a consequence, T₃ and T₄ levels were normal. The T₃ release from perifused rat thyroids under continuous stimulation with 10 mU/ml TSH was inhibited significantly (p<0.01) by 1.0×10^–6 M Ind. On the other hand, the TSH release from perifused rat pituitaries under TRH stimulation was enhanced conspicuously by Ind. It was concluded that Ind decelerated thyroid hormone release from the thyroid and accelerated TSH release from the pituitary in perifusion systems.     

Effects of thyroidectomy and thyroxine replacement on the responsiveness of the anterior pituitaries from male rats to thyrotropin-releasing hormone in vitro

Summary Thyroidectomy decreased prolactin concentrations in the anterior pituitary (AP) and serum of the male rat. The amount of basal and thyrotropin-releasing hormone (TRH)-stimulated release of prolactin by AP in vitro was lower in thyroidectomized (Tx) rats than in sham Tx rats. These results suggest that the inhibitory effects of thyroidectomy on pituitary and serum prolactin in male rats are mediated in part by the reduction of the production and spontaneous release of prolactin and the responsiveness of prolactin to TRH.     

Lesions in suprachiasmatic nuclei simulate effects of pinealectomy on prolactin release in ovariectomized and sulpiride-treated female rats

Previous studies indicate that the pineal gland alters prolactin secretion, and it was suggested that at least part of the effect of the pineal hormone melatonin on prolactin release may be mediated by the hypothalamic structures. In this study, pinealectomy and lesions of the suprachiasmatic nuclei were found to alter serum levels of prolactin in the same direction, an effect that was counteracted by daily afternoon melatonin administration. Melatonin, but not other pineal indoles, also prevented sulpiride-induced prolactin secretion in pinealectomized or suprachiasmatic nuclei-lesioned and ovariectomized rats, which suggested that the pineal gland can modulate prolactin secretion by acting through a dopamine mechanism independent of hypothalamic suprachiasmatic structures.     

Effect of experimental diabetes on estradiol binding by the anterior pituitary and hypothalamus in ovariectomized rats

Summary In diabetic rats,³H-estradiol binding by the cytosol and nuclei of the anterior pituitary was lower than normal. Changes in affinity and receptor numbers were demonstrated by Scatchard analysis. Protein synthesis in diabetic pituitaries, however, was in the normal range.     

The effects of continuous chloroform and halothane anesthesia on plasma prolactin levels in ovariectomized estrogen-treated rats

Summary In ovariectomized, estrogen-treated rats bearing indwelling aortic catheters, continuous inhalation of chloroform or halothane resulted in increases in plasma prolactin levels 10 min after the exposure to the anesthetics. The plasma prolactin levels over the subsequent 2 h, however, were not significantly different from that of the control animals.Supported by NSF Research Grant BMS 74-17332.The authors wish to express their appreciation to Mrs Cynthia Van De Walle for her outstanding assistance in the performance of the prolactin RIA and the art work.     

The lack of an effect of cholinergic agonists on anterior pituitary prolactin production in vitro

Summary The addition of dopamine to anterior pituitary incubations resulted in a marked decrease (88% for³H prolactin and 69% for RIA prolactin) in prolactin release. Incubation with the cholinergic agonists carbacol, arecoline and nicotine resulted in no significant change in prolactin secretion.Supported in part by NSF Research grant No. BMS 74-17332.The authors appreciate receiving as a gift from the National Institute of Arthritis, Metabolic and Digestive Diseases, the rat prolactin used for iodination (RP-I₂) and standards (RP-1).     

Radioimmunoassay of hormonal activity of Gobius niger L. testicular interstitial tissue in organ culture: spontaneous activity and stimulation by pituitary gland]

After the interstitial tissue was cultivated, the radio-immunoassay revealed in the media very small quantities of free testosterone but much larger quantities of testosterone conjugates as glucuronids and sulfates. Association of pituitaries increases greatly the secretion. 12-13 days precultivated pituitaires retain close to 70% of their stimulating potency.     

Plasma steroid and protein hormone concentrations in patients with benign prostatic hypertrophy and in normal men

Summary Serum levels of testosterone, FSH, LH and prolactin were measured by RIA in patients with BPH (benign prostatic hypertrophy) and in control men. The testosterone concentrations in the BPH group were significantly lower than that of the control group. Serum concentrations of FSH, LH, prolactin and estradiol, did not differ significantly in the 2 groups.     

Plasma steroid and protein hormone concentrations in patients with benign prostatic hypertrophy and in normal men.

Serum levels of testosterone, FSH, LH and prolactin were measured by RIA in patients with BPH (benign prostatic hypertrophy) and in control men. The testosterone concentrations in the BPH group were significantly lower than that of the control group. Serum concentrations of FSH, LH, prolactin and estradiol, did not differ significantly in the 2 groups.     

Etude ultrastructurale des variation cytologiques induites par la lumière sur l'adénohypophyse de la caille mâle

Summary The collective data obtained at the ultrastructural level in anterior pituitaries of male Chinese quails submitted to long daily photoperiods, confirm the cytological changes observed earlier in, at least, 2 types of cells of the gland. This cellular types may be the source of avain LH and FSH.     

Lesions in suprachiasmatic nuclei simulate effects of pinealectomy on prolactin release in ovariectomized and sulpiride-treated female rats

Summary Previous studies indicate that the pineal gland alters prolactin secretion, and it was suggested that at least part of the effect of the pineal hormone melatonin on prolactin release may be mediated by the hypothalamic structures. In this study, pinealectomy and lesions of the suprachiasmatic nuclei were found to alter serum levels of prolactin in the same direction, an effect that was counteracted by daily afternoon melatonin administration. Melatonin, but not other pineal indoles, also prevented sulpiride-induced prolactin secretion in pinealectomized or suprachiasmatic nuclei-lesioned and ovariectomized rats, which suggested that the pineal gland can modulate prolactin secretion by acting through a dopamine mechanism independent of hypothalamic suprachiasmatic structures.The authors thank Ms Karen Shashok for revising the English style. This work was supported in part by a grant GG85-0168 from the Comisión Asesora de Investigación Cientifica y Ténica. The NIAMDD, through the National Pituitary Agency, supplied the radioimmunoassay materials for prolactin determinations.     

Colon absorption of water and NaCl in the rat during lactation and the possible involvement of prolactin

Summary The absorption of water and NaCl by the ascending colon of female rats was significantly increased by prolactin treatment in virgin rats and during suckled lactation. Bromocriptine treatment of lactating rats resulted in decreased colonic absorption, suggesting that increased prolactin secretion may be responsible for the enhanced colonic absorption seen during lactation.This study was aided by NIH/Fogarty Fellowship F 05 TWO 2738 and by NSF Grant PCM-78-10348 to Professor H.A. Bern.The author is greatly indebted to Professor H. A. Bern for his support and helpful suggestions. Ovine prolactin was generously provided by NIAMDD. Professor E. Flückiger, Sandoz Ltd., kindly provided the bromocriptine used in this study. The assistance of William J. Young in taking care of the animals is greatly appreciated.     

Influence of dopamine infusion on plasma prolactin released by kidney capsule transplanted anterior pituitaries

Summary The infusion of dopamine into the renal artery resulted in decreased prolactin release from 3 anterior pituitary glands transplanted under the kidney capsule. Prolactin levels continually decreased over a 5 min period after DA infusion was terminated and thereafter approached preinfusion levels by the end of 10 min.Supported by NSF Research, grant No. 74-17332.The authors wish to express their appreciation to Mrs Cynthia Van De Walle for her outstanding technical assistance in the performance of the prolactin RIA and the statistical analyses. We also appreciate receiving as a gift from the National Institute for Arthritis, Metabolism and Digestive Diseases the rat prolactin used for iodination (RP-I₂) and standards (RP-1).     

Cellular and subcellular localization of3H-diethylstilbestrol in the pituitary,oviduct and uterus of the female rat

Summary Female rats were injected with³H-diethylstilbestrol. The pituitaries, oviducts, and uteri were removed and processed for autoradiography. The nuclear uptake and retention in these tissues appeared similar to that seen after the injection of³H-estradiol except in the pars nervosa of the pituitary gland.This study was supported by US PHS Career Development Award No. NS00164 and PHS Grant No. NS21933.     

Adenyl cyclase activity at different environmental temperatures in the isolated rat anterior pituitary membranes.

The effect of different environmental temperatures on adenyl cyclase was studied. An increase in temperature appears to increase TRH-induced activity of adenyl cyclase, and possible causes an increases sensitivity to the hormone. Cyclic AMP levels of the pituitaries showed change at different environmental temperatures.     

Adenyl cyclase activity at different environmental temperatures in the isolated rat anterior pituitary membranes

Summary The effect of different environmental temperatures on adenyl cyclase was studied. An increase in temperature appears to increase TRH-induced activity of adenyl cyclase, and possibly causes an increased sensitivity to the hormone. Cyclic AMP levels of the pituitaries showed change at different environmental temperatures.     

The influence of long term estrogen treatment on plasma prolactin levels induced by ether anesthesia in ovariectomized rats

Summary 2 methods of continuous estrogen delivery, polyestradiol phosphate injection and implantation of Silastic capsules of estradiol-17 , in ovariectomized rats induced increases in plasma prolactin in the afternoon (15.00–17.00) beginning at 1 week and continuing for 4–8 weeks. In addition these methods of estrogen treatment potentiated the ether-induced increase in plasma prolactin in the morning (9.00–11.00) beginning on week 2 and continuing for 3–8 weeks. These results indicate that estrogen activates the mechanisms that cause an afternoon surge in prolactin before potentiating a morning elevation induced by ether anesthesia.Acknowledgment. This work was supported by NIH General Research Support, grant No. RR05384-14 to Wayne State University School of Medicine. The authors also with to express their appreciation to Mrs C. Van De Walle for her expert technical assistance in the prolactin radioimmunoassay, to Dr Richard R. Gala for his advice and support of this project and to the Rat Pituitary Hormone Distribution Program of NIAMDD for the generous gift of Rat Prolactin.