Variations in guanine-binding proteins (Gs, Gi) in cultured bovine adrenal cells. Consequences on the effects of phorbol ester and angiotensin II on adrenocorticotropin-induced and cholera-toxin-induced cAMP production.
The corticotropin (ACTH) or cholera-toxin-induced cAMP production by cultured bovine adrenal cells increased progressively between days 0 and 7 of culture. Angiotensin II (A-II), which inhibited both basal and ACTH-stimulated adenylate cyclase of crude adrenal membranes, had no effect on ACTH-induced or cholera-toxin-induced cAMP production by fresh isolated cells (day 0) but progressively potentiated the stimulatory action of both effectors from day 0----1 to day 7 of culture. In contrast, phorbol ester had a potentiating effect on fresh isolated cells. Pretreatment of cells with pertussis toxin enhanced the potentiating effect of A-II on cells between 0 and 3 days of culture, but not after 7 days. ADP-ribosylation by cholera toxin (ribosylating alpha s proteins) or pertussis toxin (alpha i proteins), of adrenal membranes prepared from fresh isolated or cultured cells revealed an increase in alpha s and a dramatic decrease in alpha i, the ratios alpha i/alpha s on days 0, 3 and 7 of culture were 4, 0.6 and 0.1 respectively. These results indicate that (a) A-II had a double effect on ACTH-induced or cholera-toxin-induced cAMP production: one inhibitory mediated by Gi, the other stimulatory mediated by protein kinase C activation; this could explain the lack of apparent effect of A-II on fresh cells; (b) the progressive decrease of alpha i might be responsible for the appearance of the potentiating effect of A-II whereas the progressive increase of alpha s could explain the enhanced responsiveness to ACTH or cholera toxin of cultured cells.
Begeot
M
M
INSERM U 307, Hôpital Debrousse, Lyon, France.
Langlois
D
D
Penhoat
A
A
Saez
J M
JM
D000246:Adenosine Diphosphate Ribose / Q000032:analysis; D000311:Adrenal Glands / Q000187:drug effects / Q000378:metabolism*; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology*; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D002772:Cholera Toxin / Q000494:pharmacology*; D000242:Cyclic AMP / Q000096:biosynthesis*; D004357:Drug Synergism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D010703:Phorbol Esters / Q000494:pharmacology*
D010703:Phorbol Esters; D000804:Angiotensin II; D000246:Adenosine Diphosphate Ribose; D000324:Adrenocorticotropic Hormone; D002772:Cholera Toxin; D000242:Cyclic AMP; D019204:GTP-Binding Proteins