The effect of ACE inhibitor and angiotensin II receptor antagonist therapyon serum uric acid levels and potassium homeostasis in hypertensive renal transplant recipients treated with CsA

Background. The angiotensin II (AT II) type I receptor antagonist losartan has been reported to increase urinary uric acid and potassium excretion. Th ese effects might be beneficial in cyclosporin (CsA)-treated renal transpla nt recipients, who frequently suffer from hyperuricaemia and hyperkalaemia. Methods. In this prospective, open, randomized, two-way cross-over study we included 13 hypertensive CsA-treated patients after renal transplantation and administered either the angiotensin-converting enzyme (ACE) inhibitors enalapril or losartan. Laboratory parameters, 24-h urinary protein excretio n, and mean 24-h arterial blood pressure (MAP) were checked after 3 weeks t reatment with enalapril, after a wash-out period of 2 weeks. and before and after a 3-week treatment course with losartan. Results, Both drugs slightly reduced MAP (losartan from 97 +/- 6 to 94 +/- 9 and enalapril to 93 +/- 8 mmHg). Serum potassium levels significantly inc reased during enalapril therapy (from 4.3 +/- 0.5 to 4.8 +/- 0.4 mmol/l. P< 0.05), as did. although not significantly, uric acid concentrations (from 7 .8 +/- 1.9 to 8.2 +/- 1.8 mg/dl P=0.5). Losartan, on the contrary, only mil dly affected serum potassium (4.3 +/- 0.5 vs 4.5 +/- 0.5 mmol/l, P=0.25) an d serum uric acid decreased (from 7.8 +/- 2.4 to 7.3 +/- 1.8 mg/dl, P=0.6). Serum aldosterone and urinary aldosterone excretion were significantly red uced only during ACE inhibitor treatment, which might explain the variable effects on potassium homeostasis. Conclusion. Losartan may be a useful agent to reduce blood pressure and ser um uric acid levels in renal transplant recipients treated with CsA. Furthe rmore, in this high-risk population, the effects on serum potassium levels are less mal ked with losartan than with enalapril.