Synthesis and release of luteinizing hormone in vitro: manipulations of Ca2+ environment.
We determined if luteinizing hormone (LH) synthesis is Ca2+ dependent and coupled to LH release. We monitored LH synthesis when LH release was stimulated either by specific [gonadotropin-releasing hormone (GnRH)] or nonspecific stimuli (50 mM K+ and 2 or 20 microM Ca2+ ionophore A23187) and inhibited by Ca2+-reduced medium. LH synthesis was estimated by measuring incorporation of [3H]glucosamine (glycosylation) and [14C]alanine (translation) into total (cell and medium) immunoprecipitable LH by cultured rat anterior pituitary cells. Both GnRH (1 nM) and 50 mM K+ significantly stimulated LH release and glycosylation, but had no effect on LH translation. A23187 also stimulated LH release, but significantly depressed glycosylation of LH and total protein and [14C]alanine uptake. Deletion of Ca2+ from the medium depressed both GnRH-induced LH release and glycosylation. Addition of 0.1 mM EGTA to Ca2+-free medium not only inhibited GnRH-induced release and glycosylation of LH but also uptake of precursors and glycosylation and translation of total protein. Thus glycosylation and release of LH are Ca2+ dependent. Whether parallel changes in LH release and glycosylation reflect a cause and effect relationship remains to be determined.
D000409:Alanine / Q000378:metabolism; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002250:Carbon Radioisotopes; D005260:Female; D005944:Glucosamine / Q000378:metabolism; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D066298:In Vitro Techniques; D007986:Luteinizing Hormone / Q000096:biosynthesis* / Q000378:metabolism; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D014176:Protein Biosynthesis / Q000187:drug effects; D011506:Proteins / Q000378:metabolism; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D014316:Tritium
D002250:Carbon Radioisotopes; D011506:Proteins; D014316:Tritium; D007987:Gonadotropin-Releasing Hormone; D000001:Calcimycin; D007986:Luteinizing Hormone; D005944:Glucosamine; D000409:Alanine; D011188:Potassium; D002118:Calcium