Natriuresis and the renin axis in sodium-sensitive man.

We analysed the blood pressure, natriuretic and hormonal responses of 378 normal volunteers and 198 essential hypertensives after an intravenous infusion of 2 litres of isotonic saline and after a low-sodium diet and furosemide. Those in whom mean arterial blood pressure decreased by greater than 10 mmHg after sodium and volume depletion were considered sodium-sensitive, and those in whom a decrease of less than 5 mmHg was observed were considered sodium-resistant. Sodium-sensitive individuals had lower renin values than those who were resistant to sodium. Both normal and hypertensive sodium-sensitive individuals exhibited an 'exaggerated' natriuresis compared with resistant subjects. Sodium-sensitive subjects exhibited greater aldosterone responses to renin stimulation after volume depletion than resistant subjects. Sodium sensitivity is associated with exaggerated natriuresis as well as tighter coupling between renin and aldosterone. Relative volume expansion could account for the differences observed between sensitive and resistant individuals.