Correlation between Urinary Excretion of Arginine-Vasopressin and Renal Reabsorption of Sodium and Water

We developed an approach for quantitative assay of injected vasopressin in urine samples by ELISA under conditions of physiological suppression of hormone secretion from the neurohypophysis into the blood. In experiments on unanesthetized rats, water load (5 ml/100 g body weight) almost completely blocked secretion of arginine-vasopressin. Injection of arginine-vasopressin in a dose of 0.1 nmol/100 g body weight after water load enhanced reabsorption of solute-free water and renal excretion of Na⁺, K⁺, and Mg²⁺ by 13.3, 5.5, and 5.0 times, respectively; urinary excretion of Ca²⁺ remained unchanged. It was found that urinary excretion of arginine-vasopressin directly correlated with reabsorption of solute-free water and renal sodium excretion.

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