LHRH promotes the synthesis and release of a 87,000 Da protein (GP-87) by enriched gonadotrophs.
Protein secretion by cultured pituitary cells from 14-day-old female rats was estimated using [35S]methionine incorporation followed by either one- or two-dimensional electrophoresis and autoradiography. Stimulation of total cells or gonadotrophs by LHRH promoted the synthesis and release of a specific polypeptide (apparent molecular weight 87,000, pI = 4.6). Silver staining of cellular proteins from both gonadotroph-enriched and gonadotroph-depleted populations prepared by centrifugal elutriation revealed a high concentration of this polypeptide in the gonadotrophs and a very low level in the other cell population. This species was thus called Gonadotrope Polypeptide GP-87. Release of labeled GP-87 by gonadotrophs was both time dependent (up to 4 h) and LHRH dose dependent (from 10(-9) M to 10(-7) M) as was the release of LH. Attempts to precipitate GP-87 from the incubation medium with anti-LH antiserum were unsuccessful suggesting that GP-87 is not a 'big' form of LH. TRH neither stimulated the release of GP-87 from gonadotrophs nor from lactotrophs though it did stimulated PRL release. From these data, we conclude that gonadotrophs in culture synthesize a specific polypeptide (GP-87), LHRH stimulates both the synthesis and release of GP-87, and the pituitary cell response is peptide specific. The LHRH-induced synthesis and release of GP-87 could be an important step in the molecular processes that regulate gonadotrophin secretion.
D000818:Animals; D011232:Chemical Precipitation; D002864:Chromogranins; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005455:Fluorescent Antibody Technique; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D007120:Immunochemistry; D066298:In Vitro Techniques; D007700:Kinetics; D008715:Methionine / Q000378:metabolism; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D014176:Protein Biosynthesis; D011506:Proteins / Q000378:metabolism; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains
D002864:Chromogranins; D011506:Proteins; D007987:Gonadotropin-Releasing Hormone; D008715:Methionine