Augmentation by aprotinin of the renal response to vasopressin

Augmentation by aprotinin of the renal response to vasopressin. We contrasted the renal effects of vasopressin in Brattleboro rats with and without pretreatment with aprotinin (20,000 KIU kg-1). In both treatment groups, vasopressin injected at 3mU kg-1 sec caused in conscious rats elevation of urine osmolality and reduction of urine flow and urinary excretion of total solutes. However, these effects of vasopressin were significantly greater in aprotinin pretreated rats than in rats without aprotinin treatment. In ketamine–pentobarbital–anesthetized rats without aprotinin pretreatment, vasopressin infused at 2mU kg-1 hr-1 elevated urinary kinin excretion but did not affect urine flow rate or osmolality; in contrast, in aprotinin–pretreated rats, the same dose of vasopressin did not increase urinary kinins but caused elevation of urinary osmolality and reduction of urine flow, solute excretion, and glomerular filtration rate. Aprotinin pretreatment in anesthetized rats also blunted the rise in kinin excretion elicited by vasopressin at a higher dosage, 5mU kg-1 hr-1, but did not potentiate the vasopres-sin–induced antidiuresis. We conclude that aprotinin facilitates the expression of the antidiuretic effect of vasopressin at a low, but not at a high dosage. This effect of aprotinin may be a consequence of: (a) renal kallikrein inhibition which prevents augmentation of renal kinins in response to increased vasopressin levels, or (b) other unrecognized properties of aprotinin