GnRH-receptors of rat pituitary is a glycoprotein: differential effect of neuraminidase and lectins on agonists and antagonists binding.
The interaction of 125I-labeled gonadotropin releasing hormone (GnRH) agonist, [D-Ser-(t-Bu)6,des-Gly10-ethylamide]-GnRH, and antagonist [D-pGlu1,D-Phe2,D-Trp3,6]-GnRH with rat pituitary membranes was studied. Their binding was affected differently by pretreatment of membranes with neuraminidase and by wheat-germ agglutinin. Pretreatment of the membranes with neuraminidase abolished the specific binding of both antagonist and agonist, in a dose-response manner, with the former being less affected. Wheat-germ agglutinin affected antagonist binding slightly (22% inhibition at 40 microgram/ml) but inhibited agonist binding more markedly (50% at 40 microgram/ml). This inhibitory effect was specific since it was readily reversed by N-acetylglucosamine. Other lectins, such as concanavalin A and soybean agglutinin affected the binding of both agonist and antagonist to only a small degree. These results suggest that the GnRH-receptor of rat pituitary is a glycoprotein which contains sialic acid residue and that GnRH agonists and antagonists bind differently to the same receptor.
D000818:Animals; D002064:Buserelin; D005260:Female; D006023:Glycoproteins / Q000032:analysis*; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives / Q000378:metabolism; D037102:Lectins / Q000494:pharmacology*; D009439:Neuraminidase / Q000494:pharmacology*; D010902:Pituitary Gland / Q000032:analysis*; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000032:analysis / Q000187:drug effects* / Q000378:metabolism; D011966:Receptors, LHRH
D006023:Glycoproteins; D037102:Lectins; D011956:Receptors, Cell Surface; D011966:Receptors, LHRH; D007987:Gonadotropin-Releasing Hormone; D009439:Neuraminidase; D002064:Buserelin