Evidence for endothelin-induced renal vasoconstriction independent of ETA receptor activation.

Abstract

Experiments were designed to examine the role of endothelin (ET) receptors, specifically ETA receptors, in mediating the renal vasoconstrictor effects of ET-1 in anesthetized Sprague-Dawley rats. Intravenous infusion of ET-1 at 25 pmol.kg-1 x min-1 for 60 min produced a significant increase in mean arterial pressure (20 +/- 7%) and decreases in renal plasma flow (-60 +/- 6%) and glomerular filtration rate (-47 +/- 6%). Renal vascular resistance was significantly increased from 17 +/- 1 mmHg.ml-1 x min.g kidney wt during control period to 54 +/- 11 mmHg.ml-1 x min.g kidney wt during the experimental period. A second group of rats was infused with both ET-1 and the specific ETA receptor antagonist BQ-123 (0.1 mg.kg-1 x min-1). ET-1-induced increases in mean arterial pressure were completely blocked by BQ-123 (the average change was -7 +/- 4%). However, the renal vasoconstrictor effects of ET-1 were not affected by the antagonist, since renal plasma flow and glomerular filtration rate were again significantly reduced (-54 +/- 4 and -56 +/- 6%, respectively). Once again, renal vascular resistance was significantly increased from 16 +/- 2 mmHg.ml-1 x min.g kidney wt during the control period to 33 +/- 5 mmHg.ml-1 x min.g kidney wt during the experimental period. In a third group, infusion of BQ-123 alone produced a significant decline in mean arterial pressure (-13 +/- 2%), with no significant changes in renal plasma flow or glomerular filtration rate, thus producing a significant decrease in renal vascular resistance (15 +/- 1 vs. 11 +/- 2 mmHg.ml-1 x min.g kidney wt).(ABSTRACT TRUNCATED AT 250 WORDS)