Superoxide release by neutrophils: synergistic effects of a phorbol ester and a calcium ionophore

Exposure to combined suboptimal concentrations of 4 beta-phorbol 12-myristate 13-acetate and the calcium ionophore A23187 stimulates superoxide release from guinea pig neutrophils to rates ca. 3.5-fold greater than the sum of the rates elicited by each of the agents added separately. This effect was largely dependent upon the presence of calcium in the extracellular medium. The data are discussed in relation to recent reports concerning the interactions of phorbol-esters with cells and the mechanism of activation of superoxide release by neutrophils.