Aldosterone responsiveness to angiotensin II after sodium restriction in subjects with low renin essential hypertension.

Plasma aldosterone (PA) responses to sodium restriction (25 mEq sodium/day for 4 days) and to graded angiotensin II (AII) infusions (2, 4 and 8 ng/kg/min each for 30 min) during a low sodium intake were studied in 14 subjects with low renin essential hypertension (LREH) versus 16 normotensive subjects. The PA response to sodium restriction in relation to changes in plasma renin activity (PRA) was estimated by the ratio of PA increment to PRA increment after sodium restriction (delta PA/delta PRA). In 8 of 14 LREH subjects, whose delta PA/delta PRA ratios were normal, the PA responses to the graded AII doses were similar to those in the normotensive subjects. However, in the remaining 6 LREH subjects whose delta PA/delta PRA ratios were high the PA responses to the graded AII doses were greater. Apparently some LREH subjects, whose delta PA/delta PRA ratios after sodium restriction were high, have an abnormally enhanced aldosterone responsiveness to AII under the condition of low sodium intake.