Combination of vitamin E and vitamin C alleviates renal function in hyperoxaluric rats via antioxidant activity

Abstract

Hyperoxaluria and oxidative stress are risk factors in calcium oxalate (CaOx) stone formation. Supplement with antioxidant could be effective in prevention of recurrent stone formation. The present study aims to evaluate the protective effects of vitamin E and vitamin C in hyperoxaluric rat. The experiment was performed in rats for 21 days. Rats were divided into 5 groups as follows: control (group 1, n=8), hyperoxaluric rats (group 2, n=8), hyperoxaluric rats with vitamin E supplement (group 3, n=7), hyperoxaluric rats with vitamin C supplement (group 4, n=7) and hyperoxaluric rats with vitamin E and C supplement (group 5, n=7). Hyperoxaluria was induced by feeding hydroxyl L-proline (HLP) 2% w/v dissolved in drinking water. Intraperitoneal 200 mg/kg of vitamin E was given in groups 3 and 5 on days 1, 6, 11 and 16, while 500 mg of vitamin C was injected intravenously in groups 4 and 5 on days 1 and 11. Renal functions and oxidative status were measured. The urinary oxalate excretion was increased in HLP supplement rats, while glomerular filtration rate, proximal water and sodium reabsorption were significantly lower in group 2 compared with a control (P<0.05). Giving antioxidants significantly lower urinary calcium oxalate crystals (P<0.05). Hyperoxaluric rats had higher plasma malondialdehyde (PMDA) and lower urinary total antioxidant status (UTAS), which were alleviated by vitamin E and/or vitamin C supplement. In conclusion, giving combination of vitamin E and vitamin C exerts a protective role against HLP-induced oxalate nephropathy.

Keywords: glomerular filtration rate; hyperoxaluria; oxidative stress; vitamin C; vitamin E.

Fig. 1.

GFR (µl/g/min) (A) and ERPF (µl/g/min) (B), reabsorption of water (µl/g/min) (C) and sodium (µEq/g/min) (D) in proximal tubule of rats in groups 1−5. The data were shown as mean ± SEM. *P<0.05 compared with group 1, ^#P<0.05 compared with group 2.

Fig. 2.

COM (A) and COD (B) crystal scores from a urinalysis study of rats in groups 1−5. *P<0.05 when compared with group 1, ^#P<0.05 when compared with group 2.

Fig. 3.

Histopathology pictures of kidneys in 5 groups of rats were shown (H&E staining, mag 10 × (capital letters), inset mag 40 × (small letters). Group 1, no remarkable lesions of both glomerulus and tubules were found (A, a). Group 2, the moderate to severe tubular degeneration; marked flattened tubular epithelium and dilated lumen of proximal and distal convoluted tubules (B, b). Group 3, mild tubular degeneration and dilatation were found compared with group 2 (C, c). Group 4, mild lesions of tubular cells and protein cast deposit in lumen were found (arrow) (D, d). Group 5, no remarkable lesion of tubular cell was noted (E, e).