The effect of ACE inhibitor and angiotensin II receptor antagonist therapy on 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. These effects might be beneficial in cyclosporin (CsA)-treated renal transplant 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 excretion, and mean 24-h arterial blood pressure (MAP) were checked after 3 weeks treatment 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 increased 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 mildly affected serum potassium (4.3 +/- 0.5 vs 4.5 +/- 0.5 mmol/l, P=0.25) and 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 reduced 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 serum uric acid levels in renal transplant recipients treated with CsA. Furthermore, in this high-risk population, the effects on serum potassium levels are less mal ked with losartan than with enalapril.