Changes in ionic movements across rabbit polymorphonuclear leukocyte membranes during lysosomal enzyme release. Possible ionic basis for lysosomal enzyme release.

Abstract

Changes in the movements of Na+, K+, and Ca+2 across rabbit neutrophils under conditions of lysosomal enzyme release have been studied. We have found that in the presence of cytochalasin B, the chemotactic factor formyl methionyl leucyl phenylalanine (FMLP) induces within 30 s large enhancements in the influxes of both 22Na+ and 45Ca+2 and an increase in the cellular pool of exchangeable calcium. The magnitude of the changes induced by cytochalasin B and FMLP exceeds that induced by FMLP or cytochalasin B alone, and cannot be explained on the basis of an additive effect of the two agents. However, these compounds either separately or together produce much smaller enhancements in 45Ca efflux. The divalent cation ionophore A23187 also produces a rapid and large increase in the influxes of both 22Na and 45Ca+2 in the presence and absence of cytochalasin B. We have also found an excellent correlation between calcium influx and lysosomal enzyme release. 42K influx is not significantly affected by any of these compounds. On the other hand, a large and rapid increase of 42K efflux is observed under conditions which give rise to lysosomal enzyme release. A flow diagram of the events that are thought to accompany the stimulation of polymorphonuclear leukocytes (PMNs) by chemotactic or degranulating stimuli is presented.