Prolactin

About: Prolactin is a research topic. Over the lifetime, 22356 publications have been published within this topic receiving 609537 citations. The topic is also known as: lactotropin, & PRL,.

Central action of interleukin-1 in altering the release of TSH, growth hormone, and prolactin in the male rat.

Abstract: In order to determine the possible effects of interleukin-1 on the release of pituitary hormones by direct action on the brain, the peptide was injected into the third brain ventricle of conscious, unrestrained male rats and the effects on hormone release were compared with effects on rectal temperature. The procedure of blood sampling and intraventricular injection resulted in a significant decline in body temperature and a decrease in plasma growth hormone without alteration in the plasma level of thyroid stimulating hormone (TSH) and prolactin. Interleukin-1 injected intraventricularly at a dose of 5 ng (0.3 pmol) prevented the decline in body temperature that occurred in the saline-injected controls and resulted in a significant elevation of plasma growth hormone levels that became apparent within 15 min of injection, as well as a highly variable but significant elevation of plasma prolactin and a significant decline in plasma TSH that was observed at 30 min. The results were similar when areas under the release curves for the various hormones were calculated. On the other hand, the higher dose of 25 ng (1.5 pmole) of interleukin-1, although producing a frank pyrexia, was associated with smaller changes in hormone values, which were no longer significant for any of the three hormones. The results indicate that interleukin-1 can act in minute doses, presumably on structures near the third ventricle, to stimulate growth hormone and prolactin release and to inhibit TSH release. Apparently when frank febrile responses occur, these hormonal responses are muted for reasons that are yet to be determined. In view of the minute doses injected we favor a hypothalamic site for these effects.

Involvement of preoptic-anterior hypothalamic GABA neurons in the regulation of pituitary LH and prolactin release

Abstract: The effects of intraventricular injections of the highly specific gamma-amino-butyric acid (GABA) agonist muscimol (5 nmol/animal) on blood LH and prolactin levels were measured in ovariectomized (ovx) and in ovx estrogen-progesterone (OEP) primed rats. While the drug stimulated pituitary prolactin release in both experimental groups, pituitary LH release was significantly inhibited in the ovx animals. Muscimol was without any effect on LH levels in ovx-OEP primed rats. Bilateral implantation of tubes containing a muscimol-mannitol mixture into the medial preoptic/ anterior hypothalamic (MPO/AH) area abolished pulsatile LH release whereas blood prolactin values were elevated. The intraventricular injection of GABA (8 μmol) also reduced LH and increased prolactin levels in the blood. Measurements of catecholamine turnover rates in the MPO/AH and in the mediobasal hypothalamus (MBH) yielded reduced preoptic but unchanged hypothalamic norepinephrine (NE) and stimulated hypothalamic dopamine (DA) turnover. In view of the well known stimulatory involvement of the NE system in the mechanism of pulsatile LH release and the inhibitory effect of GABA and its agonist muscimol on pulsatile LH release, it is suggested that GABA inhibits NE release in the MPO/AH by the mechanism of presynaptic inhibition. The observation that muscimol is unable to suppress LH release in vox OEP-primed rats may indicate that those estrogen receptive neurons in the MPO/AH which mediate the negative feedback action of the steroid may use GABA as neurotransmitter and that they are the neurons which inhibit NE release. The inhibitory effect of locally implanted muscimol into the MPO/AH also supports this hypothesis. The facilitatory action of this implanted GABAergic drug on prolactin release points to the involvement of control mechanisms for the regulation of prolactin secretion which reside in the MPO/ AH. The stimulatory effect of intraventricularly injected GABA on hypothalamic DA turnover makes it likely that other than dopaminergic mechanisms are involved in mediating the stimulatory effect of GABA on prolactin release.

Effect of Nest-Deprivation on Serum Prolactin Level in Nesting Female Turkeys

Abstract: Serum levels of prolactin (PRL), luteinizing hormone (LH), progesterone and estradiol-17t1 were compared in female turkeys during various phases of their reproductive life cycle. Prolactin levels of broody turkeys were higher (2164 ± 127 ng/ml) than those of laying turkeys (468 ± 74 ng/ml), which were in turn higher than those of hens that had stopped laying (119 ± 18 ng/ml). Serum LH, progesterone, and estradiol-17� levels of laying hens were significantly higher than those of the other two groups. The levels of these hormones did not differ between broody hens and hens that had stopped laying, but were not broody (photorefractory hens). Serum prolactin levels of broody hens dropped markedly within a day of nest-deprivation and confinement to cages. Levels remained low while hens were in cages. When nests were again made available to broody hens that had been deprived of nests for 48 h, they resumed nesting within 5 mm, and serum prolactin levels then increased. In other experiments, it was found that a significant decline in serum prolactin occurred after 8, but not 4 h of nest-deprivation. After a 48 h period of cage confinement of hens, prolactin levels were seen to increase within 30 mm after hens were returned to their home pens. Levels continued to rise and had nearly reached pre-cage confinement levels by 12 h after resumption of nesting. BIOLOGY OF REPRODUCTION 23, 118-123 (1980)

Hypothesis for mammary tumorigenesis in Sprague‐Dawley rats exposed to certain triazine herbicides

Abstract: The symmetrical triazine herbicides have been used for the preemergence control of broadleaf weeds for nearly three decades. Recently, certain members of this class, primarily the chlorotriazines (substituted in the 2 position), have been shown to evoke an increased incidence of mammary tumors in female Sprague‐Dawley rats. This response was noted when these chemicals were administered in the diet for 2 yr, and most often at dietary feeding levels at or above the maximum tolerated dose (MTD). At levels exceeding the MTD the health of these animals was compromised, as manifested by toxicity‐related reduced survival that was not associated with the occurrence of mammary tumors. Mammary tumors in rats frequently occur as a result of the influence of endogenous estradiol and prolactin. Those hormones, as well as progesterone, growth‐stimulating, luteinizing, and follicle‐stimulating hormones, were measured after 24 mo of dietary administration of the chlorotriazine, simazine. The plasma hormone pattern seen i...

Regulation of Progesterone Levels during Pregnancy and Parturition by Signal Transducer and Activator of Transcription 5 and 20α-Hydroxysteroid Dehydrogenase

Abstract: The two highly related signal transducers and activators of transcription (Stats), Stat5a and Stat5b, are major mediators of prolactin signaling in both the mammary gland and in the ovary Deficiencies in Stat5b, or in both Stat5a and Stat5b, result in loss of pregnancy during midgestation and are correlated with an increase in ovarian 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD) and a decrease in serum progesterone, which normally declines only immediately before parturition To determine the relative contribution of 20alpha-HSD to progesterone metabolism and Stat5 function during pregnancy and parturition, we created a 20alpha-HSD-deficient strain of mice by gene disruption Mice deficient for 20alpha-HSD sustain high progesterone levels and display a delay in parturition of several days demonstrating that 20alpha-HSD regulates parturition downstream of the prostaglandin F2alpha receptor in an essential and nonredundant manner Moreover, 20alpha-HSD deficiency partially corrected the abortion of pregnancies associated with Stat5b deficiency, supporting the concept that prolactin activation of Stat5b is important in suppressing 20alpha-HSD gene expression and thereby allowing the maintenance of progesterone levels that are required to sustain pregnancy