Reciprocal Relation between Renin Dependency and Sodium Dependency in Essential Hypertension

To investigate the roles of angiotensin II and sodium in essential high-renin, normal-renin and low-renin hypertension, 14 patients received the competitive antagonist of angiotensin II, saralasin, during periods of sodium depletion and repletion. Blood-pressure response to saralasin was determined by the state of sodium balance. Patients from all three renin subgroups exhibited a fall in blood pressure when sufficiently sodium depleted, and an elevation in blood pressure when sodium replete or insufficiently depleted. However, those with low renin required loss of substantially more sodium (sufficient to elicit compensatory stimulation of renin) before depletion could be achieved. In patients with essential hypertension of all three renin subgroups, sodium balance determines the degree of participation of the renin-angiotensin system in sustaining high blood pressure. Even the low-renin type can become renin dependent with sufficient sodium depletion.