To investigate the role of phosphatase in O_(2~-) generation, the effects of the potent phosphoprotein phosphatase inhibitors, Calyculin A and FK506, were analyzed during phagocytosis using rat peritoneal macrophages. O_(2~-) generation was continuously measured after addition of opsonized zymosan (op. ZY) or IgG-coated zymosan (IgG-ZY). The rate of O_(2~-) generation was directly proportional to the number of macrophages, up to1-2 x 10~6 cells/ml. It was found that the rate and duration of O_(2~-) generation were markedly inhibited by Calyculin A. The addition of 100nM of Calyculin A reduced O_(2~-) generation to about one-tenth of the control value. In contrast, FK506 did not inhibit O_(2~-) generation, suggesting that calcium calmodulin phosphatase is not involved in the activation of NADPH oxidase. This rusult indicates that the process of dephosphorylation might involve activation of NADPH oxidase as a control mechanism in phagocytosis by rat peritoneal macrophages. Furthermore, since Calyculin A is an inhibitor of phosphatase 1 and 2A, it is suggested that dephosphorylation may be evoked by these phosphatases.
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