Effects of rat serum on gonadotrophin release in vitro.

Gonadotrophin release from a monolayer of cultured pituitary cells from the rat was increased by the addition of fresh rat serum or rat serum albumin to the culture medium. Similar effects were obtained when horse, chicken, lamb or porcine serum was used. Fetal bovine serum or bovine serum albumin showed a stimulatory effect on FSH and LH release but, unlike the case with rat serum, a dose-response release could not be demonstrated. In addition, fresh rat serum caused the accumulation of secretory granules in the gonadotrophs. The addition of LHRH to the culture medium also stimulated gonadotrophin release in a dose-response dependent manner. The dependence of the gonadotrophs on LHRH was markedly increased by the addition of 50% fresh rat serum to the culture medium. These results indicate that fresh rat serum contains some unknown factor(s) which 1) stimulates gonadotrophin release, 2) causes an accumulation of secretory granules, and 3) is important for maintaining secretory capacity of gonadotrophs.