Opposite effects of endothelin-1 and big-endothelin-(1-39) on renal function in rats

Bolus injections of Big-endothelin-(1-39) (Big-ET; 0.1-3.0 nmol/kg) induced a dose-dependent diuretic and natriuretic response in conscious Sprague-Dawley rats. Endothelin-1-(1-21) (ET-1; 1 nmol/kg) induced an opposite effect with almost complete renal shut down. Renal blood flow did not change with Big-ET but was reduced by half with ET-1. Although the maximal pressor responses of the two peptides were comparable the renal resistance did not change with Big-ET but increased 4-fold with ET-1. These data suggest that Big-ET may have a different mechanism of action than ET-1.