Endocrinology, Vol 110, 722-726, Copyright © 1982 by Endocrine Society

ARTICLES

Evidence that autoregulation of prolactin production does not occur at the pituitary level

L Vician, ME Lieberman and J Gorski

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.