Influence of endothelin on cardiovascular function, oxygen free radicals, and blood chemistry.

Endothelin, a peptide that is derived from vascular endothelial cells, is a potent constrictor of mammalian blood vessels in in vitro studies. Various clinical conditions have been reported to be associated with an increase in the blood and tissue levels of endothelin. In the present study, the effects of two doses (2.059 and 4.118 micrograms/kg, intravenously) of endothelin on cardiac function and contractility; blood lactate, gases, and pH levels; blood and cardiac tissue MDA levels; PMN leukocyte chemiluminescence activity; and total WBC and PMN leukocyte counts were investigated in anesthetized dogs. Hemodynamic measurements and collection of blood samples for various biochemical measurements were made before and at various intervals up to 2 hours after endothelin administration. Endothelin in the large dose (4.118 micrograms/kg) produced a prolonged decrease in the indices of cardiac contractility and cardiac function and increases in TSVR, PVR, and mean right atrial pressure. The changes in the hemodynamic parameters with the smaller dose (2.059 micrograms/kg) were similar but of smaller magnitude. Significant decreases in dp/dt at CPIP:PAW and CI and increases in TSVR and PVR were observed with the smaller dose of endothelin. There were decreases in the blood HCO3- and pH levels and an increase in H+ and blood lactate concentration and CK activity with the high dose of endothelin. No changes were observed in blood PO2 and PCO2 with either dose of endothelin. Circulating WBCs and PMN leukocytes decreased significantly with both doses of endothelin. There were no changes in the oxygen free radical-producing activity of PMN leukocytes and in the blood and cardiac tissue MDA levels. These results suggest that endothelin decreased cardiac function and cardiac contractility and increased SVR and PVR. The decrease in cardiac function and contractility may be due to ischemia from constriction of coronary arteries. The hemodynamic changes are unlikely be due to oxygen free radicals since there was no increase in the blood and cardiac tissue MDA levels and no change in the PMN chemiluminescence. These studies suggest that increases in endothelin levels in certain clinical conditions might cause added deleterious effects on cardiovascular function.