Abstract
Superoxide release from polymorphonuclear leukocytes (PMNL) stimulated by concanavalin A was enhanced by cytochalasin (Cyt) A at lower concentrations. However, Cyt A did not stimulate PMNL to release superoxide by itself. These concentrations of Cyt A did not affect the phagocytosis of diisodecyl phthalate emulsion and bacteria. The enhancing effect of superoxide release was reversible, dependent on extracellular Ca, and accompanied by the release of membrane-bound Ca.
Higher concentrations of Cyt A inhibited both superoxide release and phagocytosis irreversibly. These effects were decreased by the preincubation of PMNL with sulfhydryl (SH) agents before the addition of Cyt A and seemed to resemble those of penetrating SH-blocking agents. Cyt A did not affect the activity but the activation of NADPH oxidase. It is suggested that Cyt A acts not only as a SH-blocking agents, but has actions resembling the other cytochalasins.
