1. The effect of acetylsalicylic acid (ASA, 3 g/day for 3 days) and of indomethacin (IND, 150 mg/day for 3 days) on diuresis and on the excretion of prostaglandin E2 (PGE2) was studied in six healthy, male volunteers. After overnight deprivation the subjects received an oral water load (20 ml/kg) and hourly urine volumes were replaced by an equivalent volume of water by mouth for 4 h.
2. Pretreatment with both ASA and IND induced a comparable suppression (P<0.05 to <0.001) in the excretion of PGE2, but only IND also reduced (P<0.05) diuresis, free water clearance and the excretion of sodium. The excretion of creatinine was uninfluenced by both ASA and IND.
3. These data indicate that a mechanism other than cyclo-oxygenase inhibition is involved in the effect of IND and ASA on diuresis in man.