Caffeine stimulates Ca2 entry through store-operated channels to activate tyrosine hydroxylase in bovine chromaffin cells

Abstract

The ability of caffeine-induced store Ca2+ mobilization to activate tyrosine hydroxylase was studied in bovine adrenal chromaffin cells. Caffeine increased tyrosine hydroxylase activity over 10 min with an EC50 of 3 mM and maximum effect at 20 mM. The maximum response to caffeine was substantial, being almost one third that of the strongest agonists acetylcholine and PACAP-27, about half that for K+ and similar to that for histamine. In contrast, catecholamine secretion evoked by caffeine was small, being less than 10% of the response to strong agonists. Caffeine-induced tyrosine hydroxylase activation was not mimicked or prevented by phosphodiesterase inhibition with isobutylmethylxanthine,..