Inhibition by tosyl-L-phenylalanyl chloromethyl ketone of membrane potential changes in rat neutrophils. Correlation with the inhibition of biological activity.

A plasma membrane-associated serine esterase (protease) has previously been reported to be required during stimulation of a variety of cell types. In this study we have examined the role of such a protease on membrane potential changes using an optical probe of membrane potential 3,3'-dipropylthiodicarbocyanine iodide. The irreversible chymotrypsin-like protease inhibitor TPCK (tosyl-L-phenylalanyl chloromethyl ketone) inhibited membrane potential changes in rat neutrophils in response to phorbol myristate acetate, N-formylmethionylleucylphenylalanine and the calcium ionophore A23187 in a time- and dose-dependent manner. This inhibition was correlated with the known inhibitory effects on superoxide (O-2) generation and enzyme release (lysozyme and beta-glucuronidase). High external calcium concentrations overcame the inhibitory effects of TPCK on A23187-induced stimulation but had no effect on the inhibition of N-formylmethionylleucylphenylalanine stimulation. These results suggest that a TPCK-inhibitable activity is required for the development of the membrane potential changes that are coupled to subsequent secretory events and precede a calcium requiring activity.