title: Biosynthesis and secretion of lutropin in rat gonadotropes treated with swainsonine.
abstract: Biosynthesis and secretion of LH were investigated using primary cultures of rat gonadotropes following exposure to swainsonine, an inhibitor of N-linked oligosaccharide processing. The inhibition of terminal glycosylation by swainsonine was assessed by the increase in incorporation of [3H]mannose and the decrease of incorporation of [3H]galactose into the trichloroacetic acid-insoluble and anti-ovine LH beta immunoprecipitable fractions. This inhibitor led to an increase in cellular LH with high affinity for concanavalin A and a decrease of LH with less affinity for the lectin, although the cellular LH was not decreased. The swainsonine-treated cells accumulated highly basic LH (pI, 9.6, 10.0) in a time-dependent manner. Although the treated cells showed a decrease in the responsiveness to hormonal stimulation, there were no differences in the rate and extent of LH secretion induced by maximal stimulation with 100 nmol/l GnRH between the control and treated cells over 24 h. The accumulation of highly basic LH molecules did not result from a decrease in their secretion, since they were secreted in the presence and absence of GnRH. It is concluded that significant changes in N-linked oligosaccharide structure of LH have no effect upon its secretion.
mesh_terms: D000470:Alkaloids / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured; D005591:Chemical Fractionation; D002846:Chromatography, Affinity; D007525:Isoelectric Focusing; D007986:Luteinizing Hormone / Q000096:biosynthesis* / Q000378:metabolism; D008297:Male; D009919:Orchiectomy; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D010906:Pituitary Hormone-Releasing Hormones / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D017026:Swainsonine
chemical_list: D000470:Alkaloids; D010906:Pituitary Hormone-Releasing Hormones; D007986:Luteinizing Hormone; D017026:Swainsonine