Effect of vasopressin on prostaglandin excretion in conscious dogs

A controversy persists around the effect of vasopressin on urinary prostaglandin excretion. In an attempt to explain part of this controversy, in the present study we re-investigated the effect of vasopressin on urinary prostaglandin excretion in conscious dogs after water loading and during hydropenia. In water diuresis, during the administration of arginine vasopressin or 1-deamino-8-D-arginine vasopressin, prostaglandin excretion and urine flow decreased in parallel. Prostaglandin E2 excretion fell from 1086 +/- 454 to 353 +/- 122 and from 754 +/- 216 to 226 +/- 74 pg min-1 as urine flow decreased by 74 and 66% with arginine vasopressin and 1-deamino-8-D-arginine vasopressin, respectively. In hydropenia both arginine vasopressin and 1-deamino-8-D-arginine vasopressin increased prostaglandin E2 excretion (from 85 +/- 15 to 261 +/- 82 pg min-1; and from 115 +/- 33 to 272 +/- 66 pg min-1, respectively), while urine flow remained practically unchanged. The changes in prostaglandin F2 alpha excretion were similar to those observed with prostaglandin E2. Plasma renin activity was reduced during arginine vasopressin infusion but was unaltered during 1-deamino-8-D-arginine vasopressin infusion. These results indicate that, in the conscious dog, urine flow is a major determinant of prostaglandin excretion but they also show that when large changes in urine flow are avoided vasopressin may increase urinary prostaglandin excretion.