Mechanism of Ethyl Palmitate and Cobra Venom Factor Enhancement of Heterologous Erythrocyte Survival

Summary In this study the blood survival and organ localization in rats of intravenously injected 51Cr-labeled human erythrocytes was determined in controls and following pretreatment with ethyl palmitate, a cobra venom factor, or both. Organ distribution of labeled cells was consistent with a reticuloendothelial blockade effect for the ethyl palmitate and inhibition of hemolysis for the cobra venom factor. Erythrocyte survival was enhanced only moderately following the injection of either of these substances alone. The combined administration of ethyl palmitate and the cobra venom factor, however, resulted in marked prolongation of human erythrocyte survival consistent with a synergistic effect. This suggests that in the untreated animal, both complement-dependent hemolysis and reticuloendothelial phagocytosis compete for the removal of circulating heterologous erythrocytes. Both must be blocked simultaneously for maximum heterologous erythrocyte survival.