Role of the adrenal cortex in the natriuresis associated with vasopressin infusion

We have compared the effects of a 48-h continuous infusion of arginine vasopressin (AVP) given to four subjects (one subject studied twice) with that given to four patients lacking adrenocortical function and maintained on fixed doses of mineralocorticoid and glucocorticoid replacement therapy. Both patients and normal subjects were subjected to dietary salt and water restriction during the period of the infusion, and all participants were in balance on a low sodium diet at the start of the infusion period. Infusion of vasopressin in normal subjects was associated with an increase in fractional excretion of sodium by the kidney, which continued during the day after the infusion was stopped. The infusion was also associated with a fall in plasma aldosterone as well as falls in whole blood packed cell volume, plasma renin activity and plasma noradrenaline. Infusion of vasopressin in patients lacking adrenocortical function was associated with a smaller increase in fractional excretion of sodium by the kidney in comparison with that seen in normal subjects, and the increase in sodium excretion was confined to the period of the infusion. Mineralocorticoid activity was maintained constant during the infusion, although a fall in whole blood packed cell volume, plasma renin activity and plasma noradrenaline were noted, in similarity to the study made in normal subjects. We conclude that changes in mineralocorticoid activity are the main factors contributing to the increase in renal sodium excretion seen during, and after, the continuous infusion of vasopressin in salt- and water-restricted man.