Tissue renin angiotensin systems : theoretical implications for the development of hyperkalemia using angiotensin-converting enzyme inhibitors

In patients with renal insufficiency, as the number of functioning nephrons is reduced, potassium balance is maintained by an increase in potassium excretion in the remaining nephrons. This adaptive response is, in part, mediated by an increase in aldosterone production by the adrenal gland. Use of angiotensin-converting enzyme (ACE) inhibitors in these patients can result in hyperkalemia by suppressing aldosterone production by the adrenal gland. Inhibition of aldosterone production depends on the degree of inhibition of angiotensin II formation in the circulation as well as the degree of inhibition of angiotensin II formed locally in the adrenal gland. Recent experimental evidence suggests that the latter process may be important for the tonic regulation of aldosterone production. Because the various ACE inhibitors exhibit different degrees of ACE inhibition at the tissue level, it is reasonable to postulate that angiotensin II-dependent aldosterone production will be inhibited to a lesser degree by agents that have low tissue specificity for the adrenal gland. This feature would be most advantageous in treating patients with chronic renal insufficiency and congestive heart failure who are at risk for hyperkalemia. Therefore, the ideal ACE inhibitor should not suppress aldosterone secretion in such patients.