Intrarenal infusions of endothelin in conscious dogs: interactions with prostanoids and angiotensin II.

Endothelin (2, 5, and 10 pmol/kg/min) was infused into the renal artery of conscious dogs, producing graded and progressive reductions in renal blood flow (RBF) without initial vasodilatation, parallel reductions in glomerular filtration rate (GFR), and reduced Na+ excretion, but little change in urine flow. Pretreatment of the dogs with either ibuprofen (20 mg/kg orally) or aspirin (30 mg/kg p.o.) did not significantly alter the effects of endothelin (5 pmol/kg/min) on RBF, GFR, or Na+ excretion. However, endothelin caused antidiuresis in these cyclooxygenase-inhibited dogs, indicating that the effects of endothelin on water reabsorption were prostanoid mediated. Treatment with captopril (1.5 mg/kg + 0.5 mg/kg/h) did not significantly alter any of the responses to endothelin. The local effects of endothelin in the kidneys of conscious dogs were vasoconstriction and reduced Na+ excretion which were not mediated or modified by either angiotensin II or prostanoids.