RAT PREADIPOCYTE ADENYLYL-CYCLASE - INFLUENCE OF FAT LOCALIZATION ANDANDROGENIC STATUS

The influence of androgenic status on basal and stimulated cAMP produc tion, adenylyl cyclase activities and immunoblot quantified G(s alpha) and G(i alpha 2) subunits of the adenylyl cyclase regulatory proteins were compared in confluent preadipocytes from subcutaneous (SC) and d eep-intraabdominal (epididymal) fat deposits. Maximal cAMP response to isoproterenol was lower in SC than in epididymal preadipocytes. After castration, this site-specific difference was suppressed. cAMP respon se to 2-chloroadenosine, which was identical in the two types of pread ipocytes, was decreased by castration in epididymal cells but not in S C cells. The catalytic activity of adenylyl cyclase and its maximal re sponse to GTP were higher in epididymal than in SC preadipocytes. This response to GTP was decreased by castration in epididymal preadipocyt es while it remained unchanged in SC preadipocytes. The catalytic acti vity of adenylyl cyclase was unchanged by androgenic status whatever t he cell localization. Levels of G(s alpha) quantified by immunoblottin g were not modified whatever the androgenic status and cell origine. L evels of Gi alpha 2 were not affected by the androgenic status as well , but were lower in SC than in epididymal cells. This study shows that components of the adenylyl cyclase system in preadipocytes are differ ently regulated by the androgenic status depending on the anatomical o rigin of the cells.