Effect of indomethacin and adrenocorticotrophic hormone on renal function in man: an experimental model of inappropriate antidiuresis.

The effect of prostaglandin synthesis inhibition on basal and ACTH-stimulated adrenal and renal function was investigated in normal volunteers. Data were collected during control and experimental study periods (13 days each). Adrenocorticotrophic hormone (Cosyntropin, 80 U/day) was administered i.v. on days 8 and 9 of each period. Indomethacin (150 mg/day) was given on days 5 through 13 of the experimental period. The subjects ate a constant diet containing 9 mEq of sodium, 100 mEq of potassium, and 2,500 ml of fluid daily. Indomethacin markedly inhibited urinary PGE excretion and plasma PGE concentration. The effect of ACTH alone as compared to the effect of ACTH and indomethacin showed: plasma sodium concentration, 139 +/- 1 vs. 131 +/ 3 mEg/liter (P less than 0.01, mean +/- SEM); plasma osmolality, 287 +/- 3 vs. 270 +/- 3 mOsm/liter (P less than 0.01); free water clearance, 97 +/- 66 vs. -1100 +/- 380 ml/24hr (P less than 0.01); urine volume, 2,000 +/- 60 vs. 950 +/- 200 ml/day (P less than 0.01); and urine osmolality 282 +/- 12 vs. 720 +/- 144 mOsm/liter (P less than 0.01). We conclude that the effects of ACTH and prostaglandin synthesis inhibition interact to result in inappropriate antidiuresis.