The importance of the response of the renin-angiotensin system in determining blood pressure changes with sodium restriction.

There is controversy about the efficacy of sodium restriction in the treatment of hypertension. Short-term restriction of sodium intake in normotensive subjects causes little or no fall in blood pressure. This lack of response of blood pressure to sodium restriction appears to be due, at least in part, to a reactive rise in renin and angiotensin II. In patients with essential hypertension there is suppression of the renin-angiotensin system particularly as blood pressure becomes more severe. With sodium restriction there is less of a rise in renin and angiotensin II compared with normotensive subjects and patients have a greater fall in blood pressure compared with normotensive subjects but the effect is less in mild compared to severe hypertension. As the formation of angiotensin II can now be blocked by the use of a converting enzyme inhibitor, the combination of moderate salt restriction in conjunction with a converting enzyme inhibitor is likely to be more effective in lowering blood pressure than either treatment on its own.