Ca2+ enhancement of hemolysis induced by the topical anesthetic oxethazaine in vitro

Oxethazaine (OXZ), a potent topical anesthetic, was found to induce red blo od cell(RDC) IS sis in vitro, depending upon concentrations of OXZ, RBC and Ca2+. In a 2% RBC suspension, 100 mu M OXZ caused almost complete hemolysi s in the presence of 1.3 mM Ca2+ with only a minimal effect in its absence, while higher concentrations of OXZ (400 mu M<) produced hemolysis without Ca2+. The hemolysis induced by OXZ, plus Ca2+ nas preceded by a rapid incre ase in Ca-45(2+) uptake by RBCs, with both the hemolysis and Ca2+ uptake be ing inhibited by 1 mar CoCl2, NiCl2, and quinine. Together with the Ca2+ in flux, rapid influx of Na+ and efflux of K+ occurred, and an increasing exte rnal K+/Na+ concentration ratio inhibited both hemolysis and Ca2+ influx. M orphologically OXZ plus Ca2+ caused rapid transformation to spheroechinocyt es, the formation of blebs and the pinching-off of blebs, whereas OXZ alone produced membrane invagination. SDS-PAGE: analysis of the ghosts prepared from the RBCs treated with OXZ plus Ca2+ revealed derangement of cytoskelet al components. OXZ is a rare drug that exhibits a Ca2+ ionophore-like actio n, increasing the Ca2+ permeability of plasma membranes.