Regulation of the urinary excretion of endothelin in the rat

The regulation of the urinary excretion of endothelin (UETV) and its clinical significance has not yet been established. The present study was designed to examine the effect of angiotensin II (A-II), arginine vasopressin (AVP), and nifedipine on UETV. Anesthetized Munich-Wistar rats were infused with low (50 ng/kg/min) and high (500 ng/kg/min) doses of A-II for 30 min. Both doses significantly increased UETV, from nondetectable (ND) levels to 155 +/- 54 (P < .03) and 450 +/- 86 fg/min (P < .001), respectively. This effect was accompanied by a significant increase in urine flow (UV), from 6 +/- 1 to 67 +/- 12 and 89 +/- 10 microL/min, and in mean arterial pressure (MAP), from 139 +/- 4 to 187 +/- 5 and 217 +/- 3 mm Hg. Infusions of A-II with its nonspecific antagonist, saralasin, resulted in a further increase in UETV to 647 +/- 126 and 782 +/- 117 fg/min (P < .002), respectively. However, infusion of A-II with its specific antagonist, losartan, completely blocked its stimulatory effect on UETV. Infusion of AVP, 10 or 100 mU/kg/h, produced increases in MAP, from 134 +/- 3 to 165 +/- 7 and 203 +/- 4 mm Hg, and in UV from 6 +/- 1 to 37 +/- 6 and 97 +/- 17 microL/min, comparable to A-II, but AVP did not have a marked effect on UETV.(ABSTRACT TRUNCATED AT 250 WORDS)