SUMMARYThe Na+/Ca2+exchanger (NCX) exchanges Na+ and Ca2+bidirectionally through the forward mode (Ca2+extrusion) or the reverse mode (Ca2+influx). The present study was undertaken to clarify the role of protein kinase C (PKC) in the regulation of NCX in bovine adrenal chromaffin cells. The Na+‐loaded cells were prepared by treatment with 100 µmol/L ouabain and 50 µmol/L veratridine. Incubation of Na+‐loaded cells with Na+‐free solution in the presence of the Ca2+channel blockers nicardipine (3 µmol/L) and ω‐conotoxin MVIIC (0.3 µmol/L) caused Ca2+uptake and catecholamine release.The Na+‐dependent Ca2+uptake and catecholamine release were inhibited by 2‐[4‐[(2,5‐difluorophenyl)methoxy]phenoxy]‐5‐ethoxyaniline (SEA0400; 1 µmol/L) and 2‐[2‐[4‐(4‐nitrobenzyloxy)phenyl]isothiourea (KB‐R7943; 10 µmol/L), both NCX inhibitors. These results indicate that the Na+‐dependent responses are mostly due to activation of the NCX working in the reverse mode.In addition, we examined the effects of PKC inhibitors and an activator on the NCX‐mediated Ca2+uptake and catecholamine release. Bisindolylmaleimide I (0.3–10 µmol/L) and chelerythrine (3–100 µmol/L), both PKC inhibitors, inhibited NCX‐mediated responses. In contrast, phorbol 12,13‐dibutyrate (0.1–10 µmol/L), a PKC activator, enhanced the responses. Bisindolylmaleimide I and chelerythrine, at effective concentrations for inhibition of Na+‐dependent catecholamine release, had a little or no effect on high K+‐induced catecholamine release in intact cells or on Ca2+‐induced catecholamine release in β‐escin‐permeabilized cells.These results suggest that PKC is involved in the activation of NCX in bovine adrenal chromaffin cells.