Influence of cytoplasmic ATP reduction on catecholamine synthesis in cultured bovine adrenal chromaffin cells

Abstract

To elucidate a possible role of cytoplasmic ATP in the regulation of catecholamine biosynthesis, cultured bovine adrenal chromaffin cells were pretreated with metabolic inhibitors in the glucose-free medium, and the cytoplasmic concentration of ATP was determined by measuring the amount of ATP released by permeabilization of the plasma membranes with digitonin. Catecholamine biosynthetic activity in these metabolic inhibitor-treated cells was determined by measuring the formation of [(14)C]catecholamines from l-[(14)C]tyrosine. The cytoplasmic concentration of ATP was reduced by pretreatment of the cells with 2,4-dinitrophenol (DNP), oligomycin, carbonyl cyanide m-chlorophenylhydrazone (CCCP) and antimycin. These metabolic inhibitors reduced [(14)C]catecholamine formation without any significant alteration in [(14)C]tyrosine uptake into the cells. In addition, the formation of [(14)C]catecholamines stimulated by high K(+) or cyclic AMP was also reduced by these inhibitors. In contrast, both 2-deoxyglucose (2-DG) and NaN(3) failed to cause any substantial effect on the rate of [(14)C]catecholamine formation as well as the ATP concentration in the cell cytoplasm. While, none of these inhibitors caused a direct inhibitory action on tyrosine hydroxylase prepared from bovine adrenal medulla. The results presented here suggest the possibility that ATP in the cell cytoplasm plays an important role as a factor regulating the catecholamine biosynthetic activity in the adrenal chromaffin cell.