The in vitro hemolytic effect of diltiazem on erythrocytes exposed to varying osmolarity

Abstract

The hemolytic effect of diltiazem (a calcium channel blocker) on red blood cells (RBCs) exposed to varying osmolarity was investigated. Previous work on the in vitro hemolytic effect of verapamil shed some light on the potential for some drugs to induce hemolysis at moderate-to-high doses and in pre-existing osmotic stress. The current experimental approach used a modified red cell hemolysis assay with concentrations of diltiazem ranging from 50–1500 μM compared to drug free controls. The time-course of hemolytic effects was also investigated. In conditions representing decreasing osmolarity (dilution from 140 to 0 mM NaCl) there was a significant increase in erythrocyte hemolysis that was also dependent on diltiazem concentration (ANOVA, p < 0.05). The red cells also showed a significantly increased rate of hemolysis over 5 h with increasing concentration of diltiazem (ANOVA, p < 0.05). Overall the data suggested that diltiazem can cause hemolysis of RBCs in a predictable time- and concentration-dependent manner, and that diltiazem increases the fragility of the erythrocytes further during hypotonic osmotic stress. The mechanism of diltiazem-dependent hemolysis could involve various ion transport pathways (i.e. Ca pump, Ca Channels) and subsequent effects on cell volume control or membrane fragility.