Quantitation of the Respiratory Burst Induced in Human Neutrophils by Phorbol Myristate Acetate

A variety of particulate and soluble agonists can induce a superoxide (O₂ ⁻) respiratory burst in human polymorphonuclear leukocytes (PMNs, neutrophils). One of the most potent is the tumor promotor, phorbol 12-myristate 13-acetate (PMA), the active agent in croton oil. ^{1 - 5} The exact mechanism of PMA activation of the O₂ ⁻ generating system remains to be elucidated, but the reaction is probably initiated by the binding of PMA to specific receptors on the plasma membrane of neutrophils. ^{6 , 7} Recent in vitro studies indicate that PMA directly activates a Ca²⁺ and phospholipid-dependent kinase (protein kinase C), ⁸ and that the kinase may itself be the phorbol ester receptor or that it may be tightly associated with such a receptor. ⁹