Potentiation by ouabain of bradykinin-induced catecholamine secretion and calcium influx into cultured bovine adrenal chromaffin cells: Evidence for involvement of Na + influx associated with the bradykinin B 2-receptor

Abstract

The effect of bradykinin (BK), in the presence of ouabain, an inhibitor of Na +-K + ATPase, on catecholamine (CA) secretion was studied in cultured bovine adrenal chromaffin cells, to determine whether Na +, as well as Ca 2+, is involved in BK-receptor mediated CA secretion. BK (10 −8–10 −5M)-induced CA secretion was markedly potentiated by addition of ouabain (10 −5M), was blocked by a BK-B 2 receptor antagonist, and was decreased in Ca 2+-free medium. BK-induced increase in 45Ca 2+ influx was also potentiated by addition of ouabain. The cultured cells were first incubated with BK for 30 min in Ca 2+-free medium in the presence or absence of ouabain and then kstimulated for 15 min with Ca 2+-medium without BK or ouabain. Prior stimulation of the cells, BK induced 22Na + influx and increased Ca 2+-induced CA secretion and these stimulatory effects of BK were potentiated by added ouabain. When the cells were stimulated with BK and ouabain in Na +-free sucrose medium, the Ca 2+-induced CA secretion was greatly reduced. These results indicated that activation of the BK-B2 receptor and inhibition of the Na + pump both increase the intracellular Na + level, resulting in increase in Ca 2+ influx and CA secretion.