Effect of trifluoperazine and calmodulin on catecholamine secretion by saponin-skinned cultured chromaffin cells

We have examined the effect of trifluoperazine on catecholamine secretion by chemically skinned, cultured adrenal chromaffin cells. These cells require only ATP and calcium for secretion. Catecholamine secretion was unaffected by the drug in the presence or absence of calcium and ATP over the range 0.1 to 10 microM. At 100 microM trifluoperazine, catecholamine release was calcium and ATP independent and represented 70-80% of the total cellular content. High concentrations of exogenous calmodulin had no effect on secretion in the presence or absence of calcium. We conclude that low concentrations of the drug have no effect on secretion, while high concentrations cause non-physiological catecholamine release.