Ontogenetical variations of transcortin modulate glucocorticoid receptor function and corticotropic activity in the...

This study was aimed at investigating the influence of tissue and plasma transcortin on pituitary glucocorticoid receptor function and corticotropic activity during development. "In vivo" nuclear uptake of (3H)corticosterone was found to be increased in pituitary glands from newborn rats which, unlike that of adults, lack transcortin-like material. Immature glands incubated "in vitro" likewise showed enhanced nuclear accumulation of tracer; the magnitude of uptake being inversely related to both tissue and plasma contents of transcortin. Competition studies indicate that pituitary transcortin modulates interaction of corticosterone with receptor binding sites and, hence, may interfere with steroid translocation to the nucleus. Moreover, we found that steroid-induced inhibition of ACTH release was highest in those pituitaries which were deficient in transcortin-like molecules. We conclude that the binder plays a modulating role in pituitary glucocorticoid receptor function.