Sexual and ontogenic differences in K +-induced gonadotropin and prolactin release in vitro

Abstract

Ontogenic and sexual differences have been described in the regulation of anterior pituitary hormone relcase. In the present experiments we studied basal release and the effect of a depolarizing concentration of K + on in vitro gonadotropin and prolactin release from anterior pituitaries of male and female rats at 12,20 and 28 days of age. Basal release of LH and FSH increased with age, values obtained from female glands being significantly higher than those obtained from male glands. K +-induced release of LH did not present differences among ages, although the response in females was always greater than that in age-matched males. If K +-induced release of LH was considered in relation to basal release, infantile 12-day-old rats of both sexes, had a significantly greater sensitivity to the effect of K + in comparison to older ages, as has been described for the LH- releasing effect of LHRH and of other stimuli. K +-induced FSH release was maximal in females at 20 days of age, and in males at 28 days of age. Percentage increase relative to basal values, induced by K + was also greatest at 12 days in both sexes, although values from female glands were significantly higher than those from males. Basal and K +-induced prolactin release increased significantly with age in both sexes. Basal prolactin release was greater in females than in males at 28 days of age, and no other sexual difference was evidenced. No significant changes were observed in the amount of prolactin released by K + in relation to basal levels, whether sex or age was considered. We conclude that K +-induced hormone release from gonadotropes and lactotropes undergoes independent ontogenic variations, and that within each cell type there are marked changes related to age and sex, which may contribute to the particular regulation of anterior pituitary hormone secretion during development.