Angiotensin-converting enzyme inhibition as a therapeutic principle in Bartter's syndrome.

The effect of captopril has been investigated in four patients with Bartter's syndrome treated for 12 weeks. Baseline biochemistry showed normal serum aldosterone (mean 347 pmol.l-1) and a mean serum renin of 217 mU-l-1, and a considerable increase in serum renin during captopril treatment. Serum aldosterone decreased gradually during the study period to about half its initial value. The patients presented with a mean serum potassium of 2.5 mmol.l-1, which rose to 3.4 mmol.l-1 on captopril. Lymphocytes showed a substantial captopril-induced increase in intracellular sodium (from 15 to 22.5 mmol.l-1 on average), but no change in the potassium content. Captopril was well-tolerated. It may be an alternative to potassium-sparing diuretics for maintaining normal serum potassium levels in patients with Bartter's syndrome.