1. The urine dopamine response to intravenous frusemide (30 mg) was investigated in 15 salt replete male volunteers. The effects of oral indomethacin (100 mg) and oral carbidopa (100 mg) given before intravenous frusemide were studied in the same group of subjects.
2. Frusemide produced a significant increase in urine dopamine output within 15 min.
3. Indomethacin attenuated the natriuretic and renin responses to frusemide, but did not alter urine dopamine output.
4. Carbidopa lowered urine dopamine to undetectable levels, but did not significantly affect the natriuretic and renin responses to frusemide.
5. We conclude that urine dopamine excretion after frusemide is not directly related to increased sodium excretion or renin response and it is not mediated by the prostaglandins. In addition, dopamine does not contribute to the renal actions of frusemide under normal conditions.