The role of the microtubular system in LH/hCG receptor downregulation in rat Leydig cells.
The mechanism by which hCG-induced LH/hCG receptor 'downregulation' occurs in rat Leydig cells is unknown. To study the role of microtubules in this process we used the microtubule inhibitors vinblastine and colchicine. 200 IU hCG causes a 92-95% decrease in [125I]hCG binding to testis homogenates within 6 h after injection. Both vinblastine and colchicine prevent this loss of hCG binding. Vinblastine or colchicine did not depress the raised serum testosterone levels following hCG injection, suggesting that these agents were not having a toxic effect on the Leydig cells or on the circulation to the testis such that access of the injected hCG was impeded. The morphological observation of vinblastine-induced bundles of filamentous material in Leydig cells is evidence of a direct action on the microtubular-microfilamentous system. This data strongly implicates a role for microtubules in the process of LH/hCG receptor downregulation that occurs in the Leydig cell following large injections of hCG.
D000818:Animals; D006063:Chorionic Gonadotropin / Q000378:metabolism / Q000494:pharmacology; D003078:Colchicine / Q000494:pharmacology; D007985:Leydig Cells / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D008854:Microscopy, Electron; D008870:Microtubules / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000378:metabolism*; D011974:Receptors, LH; D013739:Testosterone / Q000097:blood; D014747:Vinblastine / Q000494:pharmacology
D006063:Chorionic Gonadotropin; D011956:Receptors, Cell Surface; D011974:Receptors, LH; D013739:Testosterone; D014747:Vinblastine; D003078:Colchicine