Permeabilization and calcium-dependent activation of rabbit polymorphonuclear leukocytes by poly-L-arginine

In the absence of extracellular Ca2+, poly-L-arginine induces little lysozyme release from rabbit polymorphonuclear leukocytes (PMNs). The polycation causes plasma membrane damage, which is evident from the release of the cytoplasmic enzyme lactate dehydrogenase (LDH). In the presence of Ca2+ concentrations higher than 0.2 mM, poly-L-arginine induces a strong lysozyme release that is superimposed on the membrane-damaging effect. The results suggest that poly-L-arginine permeabilizes the plasma membrane, enabling Ca2+ to enter the cell, which results in the exocytotic release of granule constituents. The GTP analog GTP gamma S shifts the Ca2+ requirement of exocytosis to slightly higher concentrations, whereas it completely inhibits poly-L-arginine-induced LDH release. Pertussis toxin gives a moderate inhibition, and La3+ completely inhibits poly-L-arginine-induced enzyme release. Whereas poly-L-arginine alone induces little superoxide generation in rabbit PMNs, there is a synergistic enhancement of superoxide production when GTP gamma S and poly-L-arginine are present together. Guanine nucleotides apparently have a modulating effect on the actions of poly-L-arginine on the PMN, but the nature of this effect remains to be determined.