Involvement of Vicinal Dithiols in Differential Regulation of fMLP and Phorbol Ester-Activated Phospholipase D in Stimulated Human Neutrophils☆

Abstract In the human neutrophil, the fMLP-activated phospholipase D (PLD) was entirely calcium and tyrosine kinase dependent, but protein kinase C independent. An opposite regulation was observed with phorbol ester PMA, since the phospholipase D activity was mostly calcium insensitive, tyrosine kinase independent, but protein kinase C dependent. The arsenical compound, phenylarsine oxide (PAO), which reacts with vicinal sulhydryl groups, activated twofold at one minute the PMA stimulated-PLD activity, whereas it inhibited half of the fMLP-activated PLD after a time lag of 30 sec. Our data indicate that PAO acted on a mechanism regulating the balance between fMLP-activated and PMA-activated phospholipase D activity. Noteworthy, PAO similarly inhibited fMLP and PMA-induced O 2 − · production.