Combination Therapy with Losartan and α-Tocopherol in Acute Ureteral Obstruction-Induced Renal Excretory Dysfunction and Acidification Defect

Background: Previous study by the authors showed that a-tocopherol prevents oxidative stress but would not improve depressed excretory variables in post-obstructed kidney (POK) after release of 24-h unilateral ureteral obstruction (UUO). This study is a supplementary investigation on the effects of a-tocopherol combined with an antagonist of angiotensin-II type-1 (AT(1)) receptor on renal dysfunction following release of acute UUO. Methods: The left ureter was ligated in different groups of male Sprague-Dawley rats that received normal saline, losartan or losartan/a-tocopherol (n=6 in each group). After releasing 24-h UUO, urine of each kidney was separately collected under paraffin during 1-3 h of post-release period and then both kidneys were removed for measuring malondialdehyde (MDA) and ferric reducing/antioxidant power (FRAP). Results: Losartan-treatment decreased MDA and increased FRAP, creatinine-clearance and sodium-reabsorption in POK, while co-treatment with losartan and a-tocopherol not only augmented improvement in these variables but also elevated potassium-excretion, free-water reabsorption and urine-osmolality. However, UUO-induced fall in urinary pCO(2) and rise in pH and bicarbonate-excretion of POK were ameliorated equally with losartan and losartan/a-tocopherol. Conclusion: Activation of AT(1)-receptor contributes to the development of renal distal acidification defect induced by acute ureteral obstruction. The co-treatment with losartan and a-tocopherol showed that their effects on preventing oxidative stress along with ameliorating glomerular filtration and tubular fluid-delivery in POK could lead to improvement in tubular transport of sodium and potassium as well as urine-concentrating ability at the early post-release period.