Prolactin Production by Rat Pituitary in vitro . ∗ ‡

Abstract

Summary

Anterior pituitary explants from female immature, mature and postpartum lactating rats were cultured in vitro on “199” or Trowell T-8 medium at 35 ± 1°C for periods of 6-14 days. Medium was assayed for prolactin by the intradermal pigeon crop method. Pituitary explants from mature female rats, gassed continuously with 95% O₂ − 5% CO₂ released 5-10 times more prolactin into medium each day than explants exposed only to air atmosphere. The amount of prolactin per AP recovered each day from the culture medium, under continuous gassing, was 2-3 times greater than that present in a fresh AP prior to culture. This proves that prolactin was actively synthesized and released and not merely “leached” out from AP explants. Explants from immature rats elaborated about half as much prolactin per AP per day as explants from mature rats, and ex-plants from lactating rats about twice as much as explants from mature rats. Assays of some explants at the end of culture revealed a low prolactin content, indicating rapid synthesis and release. Histological examination of ex-plants at termination of culture showed that tissue exposed to continuous gassing was almost entirely viable, whereas tissue exposed to air atmosphere had only a thin outer rim of living cells. These results demonstrate that prolactin can be produced in large amounts when AP tissue is cultured in vitro.