title: Evidence that autoregulation of prolactin production does not occur at the pituitary level.
abstract: PRL production in primary cultures of rat pituitary cells was examined for evidence of autoregulation. The kinetics of PRL accumulation in the culture medium were linear (r = 0.993) over a 20-fold range of PRL concentrations (85-1800 ng/ml). The addition of 0.01-1000 ng/ml biologically active ovine PRL for 2 h had no effect on the rate of secretion or the intracellular levels of PRL. The functional integrity of the cells was verified by the demonstration that estradiol (10(-8) M) caused a 3-fold increase in both PRL synthesis and secretion. Ergocryptine (10(-8) M) inhibited PRL secretion by 57% (P less than 0.001), and this response was modulated by pretreatment with estradiol. Increasing concentrations of endogenously secreted PRL did not detectably alter the rate of incorporation of [35S]methionine into cellular PRL in control or ergocryptine-treated cells for up to 8 h. These results indicate that autoregulation of PRL does not operate directly at the level of the pituitary.
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004873:Ergolines / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D007700:Kinetics; D010902:Pituitary Gland / Q000187:drug effects / Q000502:physiology*; D011388:Prolactin / Q000378:metabolism* / Q000494:pharmacology; D051381:Rats
chemical_list: D004873:Ergolines; D004958:Estradiol; C100269:ergocryptine; D011388:Prolactin