LH biosynthesis and secretion in rat anterior pituitary cell cultures: Stimulation of LH glycosylation and secretion by GNRH and an agonistic analogue and blockade by an antagonistic analogue

Abstract

In rat anterior pituitary cell cultures GnRH (1nM) stimulated a progressive increase in LH release into the medium from 1 to 8 h of incubation, while cellular LH showed a corresponding decrease. GnRH (1nM) neither modified the uptake nor the incorporation of [3H]-glucosamine and [3H]-proline into total protein. The incorporation of [3H]-proline into cellular LH also was unaffected by GnRH. In contrast, GnRH stimulated a 3 to 4-fold increase in [3H]-glucosamine incorporation into cellular LH. The agonistic analogue, [des GlyNH210]-LHRH ethylamide, mimicked the GnRH effects and was 5 to 6 times more potent than GnRH. The antagonistic analogue, [D-Phe2, D-Phe6]-LHRH blocked the GnRH-stimulated effects. These results suggest that GnRH and agonistic analogues may preferentially regulate turnover or synthesis of the carbohydrate moiety of LH.