title: Degradation of human choriogonadotropin in preovulatory rat granulosa cells and in follicular fluid.
abstract: The catabolism of human choriogonadotropin (hCG) in rat preovulatory granulosa cells and follicular fluid was studied in order to elucidate the mechanisms responsible for the removal of receptor-hCG complexes. Rats pretreated with pregnant mare serum gonadotropin (PMSG) were injected i.v. with 125I-labelled hCG with or without unlabelled hCG a few hours before the surge of endogenous preovulatory gonadotropin. The radioactive components of granulosa cells and of follicular fluid were characterized by filtration through Sepharose-6B gel. Granulosa cells catabolized receptor-bound 125I-hCG to hormone sub-units; however, the rate of catabolism in vivo was relatively slow. Receptor-125I-hCG complex also appeared in the follicular fluid. Binding of 125I-labelled hCG to receptor molecules of follicular fluid in vivo was time-dependent and it was inhibited by smaller amounts of unlabelled hCG than the binding, in vivo, of 125I-labelled hCG to the receptors of granulosa cells. Both follicular fluid and granulosa cell homogenate, in vitro, catabolized 125I-labelled hCG to hormone sub-units.
mesh_terms: D000818:Animals; D001665:Binding Sites; D006063:Chorionic Gonadotropin / Q000378:metabolism*; D002850:Chromatography, Gel; D005260:Female; D006107:Granulosa Cells / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D010053:Ovary / Q000378:metabolism*; D010060:Ovulation; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000378:metabolism
chemical_list: D006063:Chorionic Gonadotropin; D007457:Iodine Radioisotopes; D011956:Receptors, Cell Surface