Dual effects of antidiuretic hormone on urinary prostaglandin E2 excretion in man.

To evaluate the relationship of renal prostaglandin synthesis to urine-concentrating mechanisms, 14 healthy subjects received antidiuretic hormone (ADH) and the nonpressor ADH analog desamino-d-arginine vasopressin (dD'AVP). Endogenous ADH was increased by water deprivation. Urinary prostaglandin E2 (PGE2) was measured by RIA and by bioassay. ADH, dD'AVP, and dehydration each reduced urinary volume by a similar amount (from 582 +/- 66 to an average of 141 +/- 13 ml/4 h) and similarly increased osmolality (from 231 +/- 13 to 721 +/- 31 mosmol/kg). Dehydration and dD'AVP reduced PGE2 from 44 +/- 4 to 25 +/- 5 and 30 +/- 5 ng/4 h, respectively (P less than 0.01), suggesting an inverse correlation of PGE2 with urine osmolality (r = -0.48; P less than 0.005). In contrast, ADH increased urinary PGE2 to 102 +/- 23 ng/4 h (P less than 0.02). Infusions of another vasoconstrictor peptide, angiotensin II, to six of the subjects doubled urine osmolality and also increased urinary PGE2 excretion. These data do not support the theory that the antidiuretic effect of ADH enhances PG synthesis; instead, the data indicate that ADH has two effects on PGE2 excretion: 1) stimulation, presumably by pharmacological pressor activity, and 2) inhibition by antidiuresis.