EFFECT OF ADENOHYPOPHYSEAL PARS TUBERALIS SECRETIONS ON PARS-DISTALISPROLACTIN LIBERATION

Evidences presented indicating that factors produced by the pars tuber alis (PT) affect the prolactin the pars distalis (PD). The effect of t he secretion products of bovine PT cells in culture medium was checked on dispersed PD cells of rats. PD cells were assayed in incubations o f 30 minutes and superfusion experiments. When medium was obtained fro m total PT cells, the addition of 9 mu g of protein was needed to reac h the major stimulation of prolactin liberation. However, when the med ium from 50-60% Percoll gradient fractions was used, only 4 mu g of to tal protein were required. The partial purification of such medium by Sephadex G50 produced the same effect on the liberation of prolactin b y PD cells with 80 ng of total protein. The active factor/s should hav e a molecular weight higher than 30 kDal. The results obtained suggest , at least for the prolactotrophic cells, that PD could be the effecto r organ for some of the secretory product(s) of PT.