Effects of cytochalasin B on endocytosis and exocytosis.

The complex effects of cytochalasin B on endocytosis and exocytosis are reviewed. Cytochalasin B inhibits phagocytosis by both mononulcear phagocytes and polymorphonuclear leukocytes but it does not affect the micropinocytic activity of mononulear phagocytes and other cell types. Cytochalasin B causes increased selective release of acid hydrolase from phagocytic cells but its effect on other secretory cells is more variable, stimulating secretion by some cell types, inhibiting secretion in others and having no effect at all in some instances. The possible mechanisms of action of cytochalsin B are discussed with particular emphasis being placed on its effect on the activity of various protein components of cellular contractile systems. We suggest that many of the biolgoical effects of cytochalasin B may be accounted for by such effects.