1. Measurements of urinary aldosterone excretion and of peripheral venous plasma concentrations of aldosterone, Cortisol and corticosterone have been made in hypertensive and normotensive patients after a sodium load and after dietary sodium restriction and ambulation.
2. Plasma concentrations of aldosterone, Cortisol and corticosterone did not differ significantly between the two groups of patients, but the rise in urinary aldosterone excretion was significantly greater in normotensive than in hypertensive patients after sodium restriction.
3. Division of the hypertensive patients into two groups according to the response in plasma renin on sodium restriction did not disclose any significant differences between responders and non-responders in respect of aldosterone or Cortisol, but the plasma corticosterone rose more in normotensive patients after sodium depletion than in the unresponsive hypertensive patients.
4. It is concluded that both the rise in plasma renin and in aldosterone excretion rate are blunted in hypertensive patients after sodium restriction. It is suggested that this may be due to a rise in total body sodium in hypertensive patients.
5. Differences in aldosterone excretion rate are not reflected in the values of peripheral venous concentrations, presumably because of the short-term rise in plasma aldosterone which results from ambulation.