Stereoselective renal effects of the loop diuretic ozolinone in the anesthetized dog

The renal effects of i.v. injections of (+/-)-ozolinone, its enantiomers (-)-ozolinone and (+)-ozolinone and its prodrug (+/-)-etozoline, were compared with those of furosemide, in pentobarbital anesthetized dogs. Renal blood flow (electromagnetic flow-meter) and glomerular filtration rate (polyfructosan clearance) were assessed on the left denervated kidney together with renin secretion and urinary electrolyte excretion. (-)-Ozolinone (15.5 mg/kg i.v.) behaves as a stereoselective loop diuretic equipotent to 20 mg/kg of furosemide and 45 mg/kg of (+/-)-ozolinone; (+)-ozolinone induced only minor salidiuretic effects. Both ozolinone enantiomers markedly increased the renal blood flow and decreased the filtration fraction, suggesting that the vosodilating effect predominates on the efferent glomerular arterioles. (-)-Ozolinone also induced an acute rise in renin secretion. The inhibition of prostaglandin synthesis (indomethacin or meclofenamate) prevented renin hypersecretion in response to (-)-ozolinone and modified its salidiuretic effects but had no effect on the vascular response. The inhibition of the kallikrein-kinin system by aprotinin had no effect on the overall renal response to (-)-ozolinone. The inhibition of the renin-angiotensin system by captopril decreased blood pressure, prolonged the (-)-ozolinone-induced decrease in renal vascular resistance and increased renin secretion. Our results demonstrate that the loop diuretic, ozolinone, induces stereoselective and prostaglandin-dependent renin secretion, which is involved in the regulation of intra-renal hemodynamics.