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.     

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.     

Effects of intracerebroventricular injections of angiotensin II on prolactin plasma levels in the Rhesus monkey

Summary Intracerebroventricular injections of angiotensin II (A II) induced a sharp and dose-dependent increase in plasma prolactin (PRL) levels in the awake Rhesus monkey. Our results suggest that in primates, A II may be involved in the mechanisms controlling PRL secretion.Acknowledgments. We thank Mrs. J. Arsaut and D. Verrier for excellent technical assistance. This work was supported by grants from INSERM (CRL No. 78.1.2656), DGRST (77.7.9654) and CNRS (ERA 493).     

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.     

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.     

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).     

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.     

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.     

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.     

The effects of microinjection of carbachol or hemicholinium into the amygdala on the levels of plasma and adrenal corticosterone in rats

Microinjections of 0.4 microgram of carbachol into the amygdala caused a rise of corticosterone (CS) in the morning when the prestimulating level of CS was lower. But the same procedure with a larger dose had no effect in the afternoon, when the prestimulating level of CS was higher.     

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.     

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).     

Hyperprolactinemia and estrogen-induced rhythms in LH and prolactin release in the ovariectomized rat

Short-term (9 days) hyperprolactinemia induced by pituitary grafts reduced basal plasma LH levels in ovariectomized rats whereas long-term (31 days) grafts increased basal LH levels. Although long-term grafts inhibited estradiol-induced prolactin surges, hyperprolactinemia had no effect on the LH surge. It is concluded that the estrogen-treated ovariectomized rat is not suitable for studying the effects of hyperprolactinemia on LH release.     

Effect of benzimidazole on nicotinamide adenine dinucleotide phosphate phosphomonoesterase activity in wheat leaves.

Nicotinamide adenine dinucleotide phosphate phosphomonoesterase was isolated and partially purified from wheat (Triticum aestivum L. var. Selkirk) leaves. The enzyme had KNADP value of 1.4 X 10(-4) M and a pH optimum of 5.9. In vitro activity of this enzyme was unaffected by precursors of NAD (nicotinamide and nicotinic acid) or cytokinins (kinetin and benzimidazole). However, when detached wheat leaves were treated with solutions of these compounds, the precursors lowered the specific activity while the cytokinins enhanced the activity. It is suggested that spatial separation and compartmentation of the enzyme and its substrate NADP account for the similar effect of benzimidazole on both.     

Hyperprolactinemia and estrogen-induced rhythms in LH and prolactin release in the ovariectomized rat

Summary Short-term (9 days) hyperprolactinemia induced by pituitary grafts reduced basal plasma LH levels in ovariectomized rats whereas long-term (31 days) grafts increased basal LH levels. Although long-term grafts inhibited estradiol-induced prolactin surges, hyperprolactinemia had no effect on the LH surge. It is concluded that the estrogen-treated ovariectomized rat is not suitable for studying the effects of hyperprolactinemia on LH release.     

Cytochemical gradients and mitochondrial exclusion in the apices of vegetative hyphae

Summary Apical maximal acidity (shown by subapically increasing pH) and maximal concentration of inorganic phosphate (shown by a subapically decreasing gradient of yellow phosphomolybdate) contrast with the subapical, mainly mitochondrial sequestration of calcium ions. Such gradiential control of calcium concentration appears to be the requisite for the Ca⁺⁺ sensitive gelation of the apical hyaloplasm preventing the mitochondria from entering into this continuosly elongating zone of growing hyphae.The support of the founds National Suisse de la Recherche Scientifique is acknowledged and we thank Miss E. Herz for her technical assistance.     

The effects of microinjection of carbachol or hemicholinium into the amygdala on the levels of plasma and adrenal corticosterone in rats

Summary Microinjection of 0.4 g of carbachol into the amygdala caused a rise of corticosterone (CS) in the morning, when the prestimulating level of CS was lower. But the same procedure with a larger dose had no effect in the afternoon, when the prestimulating level of CS was higher.     

Evidence that a 'critical period' is involved in early estrogen-induced LH- and FSH-release during the estrous cycle in the rat

LH- and FSH-release, which occurred in the afternoon of diestrus 1 following estradiol benzoate administration in the morning of estrus, was completely prevented by pentobarbital, when injected on diestrus 1 at 13.30 h.