Effects of phorbol esters and forskolin on basal and histamine-induced accumulation of inositol phosphates in cultured bovine adrenal chromaffin cells.
The effect of phorbol esters and forskolin pretreatment on basal and histamine-induced accumulation of inositol phosphates and catecholamine release was examined in cultures of bovine adrenal chromaffin cells. Histamine caused a dose-dependent, Ca2+-dependent accumulation of total inositol phosphates with an EC50 at approximately 1 microM and an eight- to 10-fold increase at 100 microM within 30 min of incubation. Histamine (10 microM) also caused the release of cellular catecholamines amounting to some 2.8% of cellular stores released over a 20-min period. Both the inositol phosphate and catecholamine responses were completely blocked by the H1-antagonist mepyramine and were insensitive to the H2-antagonist cimetidine. Examination of the time course of accumulation of the individual inositol phosphates stimulated by histamine revealed an early and sustained rise in inositol 1,4-bisphosphate content but not inositol 1,4,5-trisphosphate content at 1 min and the overall largest accumulation of inositol monophosphate after 30 min of stimulation. Pretreatment with the tumor-promoting phorbol ester phorbol 12-myristate 13-acetate (PMA) resulted in a dose-dependent, time-dependent inhibition of histamine-induced inositol phosphate formation and catecholamine secretion. In this inhibitory action, PMA exhibited high potency (IC50 of approximately 0.5 nM), an effect not shared by the inactive phorbol ester 4-alpha-phorbol 12,13-didecanoate. Pretreatment with forskolin, on the other hand, only marginally inhibited the histamine-induced inositol phospholipid metabolism and catecholamine secretion. These data suggest that protein kinase C activation in chromaffin cells may mediate a negative feedback control on inositol phospholipid metabolism.
Wan
D C
DC
Department of Biochemistry, University of Melbourne, Parkville, Victoria, Australia.
Bunn
S J
SJ
Livett
B G
BG
D000313:Adrenal Medulla / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D002927:Cimetidine / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology*; D004837:Epinephrine / Q000378:metabolism; D006632:Histamine / Q000494:pharmacology*; D007295:Inositol Phosphates / Q000096:biosynthesis*; D007700:Kinetics; D009638:Norepinephrine / Q000378:metabolism; D010703:Phorbol Esters / Q000494:pharmacology*; D011738:Pyrilamine / Q000494:pharmacology; D013403:Sugar Phosphates / Q000096:biosynthesis*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D007295:Inositol Phosphates; D010703:Phorbol Esters; D013403:Sugar Phosphates; D005576:Colforsin; D002927:Cimetidine; D006632:Histamine; D011738:Pyrilamine; D013755:Tetradecanoylphorbol Acetate; D009638:Norepinephrine; D004837:Epinephrine