Abstract
Renal hemodynamic and natriuretic effects of bumetanide and furosemide were studied by clearance and micropuncture methods in cats. Furosemide (0.04-5.0 mg/kg i.v.) effects increased with increasing doses up to a maximal fractional sodium (FEna) and water (V/GFR) excretion of 23%. GFR and superficial single nephron GFR remained constant. Renal blood flow (RBF) increased up to 45% over control. A preferential increase in outer cortical RBF occurred at 5.0 mg/kg. Bumetanide (0.001-0.14 mg/kg i.v.) raised FEna and V/GFR maximally by 26%. Only at a supramaximal dose (0.69 mg/kg) did bumetanide raise RBF and depress filtration fraction. Probenecid (50 mg/kg i.v.) failed to block the natriuretic effect of bumetanide (0.025 microgram/kg-min) when infused into one renal artery but abolished the natriuretic action of furosemide (1.0 microgram/kg-min). Probenecid failed to displace the dose-response curve for bumetanide.
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