PRL Stimulation Research Articles

Inhibitory effects of cysteamine on neuroendocrine function.

The action of cysteamine on anterior pituitary hormone secretion was studied in vivo using conscious, freely moving male rats and in vitro using anterior pituitary cells in monolayer culture. Administration of 500 micrograms cysteamine into the lateral cerebral ventricles of normal rats caused the complete inhibition of pulsatile GH secretion for a minimum of 6 h. This treatment also significantly decreased plasma concentrations of LH for at least 6 h in orchiectomized rat, TSH in short-term (0.5 month) thyroidectomized rats, and PRL in long-term (6 months) thyroidectomized rats. The in vivo stimulation of GH, LH, TSH and PRL with their respective releasing hormones 60 min after administration of cysteamine was not different from the response observed in rats pretreated with saline except for PRL where cysteamine pretreatment significantly inhibited the expected PRL increase. In vitro, 1 mM cysteamine decreased basal and TRH stimulated PRL release while not affecting basal or stimulated GH, LH, TSH and ACTH secretion. These data demonstrate the dramatic and wide-ranging effects of cysteamine on anterior pituitary hormone secretion. This action appears to be mediated through hypothalamic pathways for GH, LH and TSH and through a pituitary pathway for PRL.

The lack of effect of bupropion HCL (Wellbatrin) on the secretion of growth hormone and prolactin in humans

The effect of bupropian HCL (Wellbatrin), a new anti-depressant, on the secretion of GH and PRL in healthy male subjects and male hyperprolactinaemic patients was studied. The study was a randomised double-blind test in which 6 subjects and 6 patients who had been treated with neuroleptics were each, in accordance with the random plan, treated once with placebo and once with 200 mg bupropion p.o.. After administration of the test substance, blood was drawn to measure bupropion, GH and PRL up to 240 minutes thereafter. Neither in the healthy men nor in the patients could a specific effect of bupropion on the secretion of CH be shown in comparison to placebo although bupropion in all subjects and patients was well reabsorbed. As opposed to the results of Stern et al. (5), no change in the secretion of PRL was measured in either the healthy subjects or the hyperprolactinaemic patients. In addition, no change in the TRH-induced stimulation of PRL could be measured. The results of the present study offer no positive contribution towards an explanation of the mechanism of bupropion.

Pain relief in childbirth and its consequences for the infant

species. may stimulate development of mammary carcinoma in male and/or female animals. In treated rats. this is usually accompanied by higher (males) or lower (females) incidences of benign mammary tumors, as compared with the corresponding controls. The speciesspecific neuroendocrine system. i.e.. estrogen-dependent stimulation of PRL seLretion appears to be of great importance in the pathogenesis of mammary tumors in mice and rats. On the other hand, stimulation of mammary tumors in dogs by certain progestogens or progestogen-estrogen combinations seem to be related to high mammary proliferative activity of these compounds in the dog and their stimulatory effect on highly mammotrophic canine GH. In total contrast to the sittiation in mice and rats. !ong-term treatment of the dog with high doses of estrogens does not stimulate mammary tumor development in spite of their ability to stimulate PRL secretion in this species. Similarly, in the monkey and man certain sex steroids (high doses) may stimulate PRL secretion. However, in the monkey. steroid-related mammary tumors are not observed. even after long-term treatmr’nt wath high doses of estrogens. progestogt ns and their combinations. Moreover, cc Intraceptive use appears to decrease the rjsk OI benign breast tumors in women. and after two decades of extensive use of contraceptive steroids, the evidence weighs against an association of these preparations with human breast cancer. These findings indicate that, with regard to the develop rr,ent of mammary tumors as an undesirable effect of contraceptive steroids. not otlly the species-specific neuroendocrine s! stem (e.g. stimulation of PRL and/or GH secretion) but also the susceptibility of certain species, strains or individuals seems to play a great role. This clearly illustrates the hmitations inherent in the extrapolation to man of data on steroid-related mamman tumors in various experimental animals.

Effects of synthetic gestagens on serum prolactin and growth hormone secretion in amenorrheic patients.

Long-term application of synthetic gestagens to monkeys and dogs has been reported to induce benign hyperplasia and nodules in the mammary gland of these animals. The underlying mechanisms might be the increase of (GH) growth hormone serum concentrations observed after progestational steroid administration. Since (PRL) prolactin has been implicated in the etiology of human breast cancer this study was initiated to investigate the effect of synthetic gestagens on PRL and GH secretion in women. Amenorrheic women were treated with either (NG) norgestrel or (NETA) norethisterone acetate or (MPA) medroxyprogesterone acetate to induce withdrawal menstrual bleedings. Before and 7 days after gestagen therapy a standardized PRL stimulation test using (MTCL) metoclopramide was carried out. PRL as well as GH was measured by means of homologous radioimmunoassays. Gestagen application resulted in a significantly increased response of PRL after MTCL administration. Basal serum GH concentrations remained unaffected by such manipulations. The data presented indicate that gestagens might play a role in PRL secretion. If lactogenic hormones at all are involved in proliferative changes of the human mammary gland this might be rather due to alteration of PRL than GH secretion. (authors) (summary in GER)

Hypothalamic catecholamine effects on plasma levels of prolactin and growth hormone in sheep.

The relationship between hypothalamic catecholamines and anterior pituitary hormone secretion was studied in mature cyclic ewes by the infusion of phenoxybenzamine, and of L—DOPA to alter hypothalamic catecholomines. The treatment effects were assessed by measuring plasma levels of prolactin (Prl) and growth hormone (GH). In addition, an arginine stimulation of Prl and GH was used in combination with phenoxybenzamine and L—DOPA to provide a more sensitive test to possible inhibitory effects of the catecholamines. In positive control experiments with arginine, it was found that the Prl and GH responses to arginine were similar whether arginine was infused on different days, or when two arginine stimuli were administered on the same day in the same group of sheep. The intracarotid infusion of phenoxybenzamine (0.5 mg/kg) resulted in an increase in plasma levels of Prl within 15 min and of GH at 45 min. The treatment with arginine (0.5 g/kg) and phenoxybenzamine (0.5 mg/kg) combined appeared to produce addit...