Reduction by indomethacin of furosemide effects in the rabbit

The effects of furosemide on urine flow, sodium and potassium excretion and on plasma renin activity (PRA) were studied in anesthetized rabbits with and without pretreatment with indomethacin 5 mg/kg. Furosemide caused a 10-fold increase in urine flow and in sodium excretion, and a 2-3 fold increase in PRA. Pretreatment with the prostaglandin synthesis inhibitor, indomethacin, reduced the effects of furosemide on diuresis and on electrolyte excretion by over 80% (p less than 0.01) and PRA did not increase over the initial level. The results suggest that the effects of furosemide on PRA and on urinary sodium excretion may be related to the intrarenal activation of the prostaglandin system.