Experimental study on the inhibitory effect of epigallocatechin gallate on renal calcium oxalate crystal formation

Abstract

Objective To compare the effects of different dosages of epigallocatechin gallate (EGCG) in calcium oxalate stone rate, to expolre content differences in malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT) and calcium oxalate crystal deposition. Methods Fifty rats were randomly divided into 5 groups: normal control group, calcium oxalate kidney stone model group and different doses of EGCG intervention group. The control group was permitted to drink purified water freely; model group was given 2 ml stone liquid that was prepared with 1% ethylene glycol and 2% ammonium chloride by the lavage. In the EGCG intervention groups, daily doses of 0.1% EGCG (10, 30, and 50 mg/kg) were given introgastrically on the basis treatment in the model group. Twenty-eight days later, the rats were sacrificed and the right kidney was prepared into homogenate. The thiobarbituric acid (TBA) method was used for the determination of MDA. The xanthine oxidase method was applied to detect SOD activity. CAT activity was tested by ultraviolet spectrophotometry. The DTNB method was used to determine GSH-Px activity. The left kidney tissue was stained by HE method, and crystal deposition was observed by polarizing microscopy. Results In the blank control group, MDA concentration was (2.74±0.47) μmol/L, SOD activity (541.71±10.61) Nu/g, CAT activity (44.49±3.45) U/g and GSH-Px activity (41.61±2.50)×103 U/g·protein. As compared with the blank control group, MDA concentration of calcium oxalate kidney stones in the model group was increased significantly, while the activity of SOD (332.44±12.01) Nu/g, CAT (32.15±1.99) U/g and GSH-Px (21.36±1.58)×103 U/g·protein was significantly decreased (P=0.009). In the low-dose EGCG group, the activity of SOD, CAT and GSH-Px was (517.41±28.37) Nu/g, (34.42±2.55) U/g and (23.94±2.95)×103 U/g·protein respectively, that in the middle-dose EGCG group (545.04±23.84), (35.42±2.61) and (25.10±2.64) respectively, and that in the high-dose EGCG group (550.58±16.55) Nu/g, (35.40±2.39) U/g and (26.67±1.93)×103 U/g·protein respectively. As compared with the model group, SOD, GSH-Px and CAT actively was increased in the EGCG groups (P=0.005). The calcium oxalate crystal deposition in the renal tissue was negatively correlated with the dose of EGCG interference (r=-0.483, P= 0.008). Conclusion There were significant differences in MDA, SOD and GSH-Px contents in calcium oxalate stone rats treated with different doses of EGCG, which indicated that EGCG could reduce the formation of calcium oxalate kidney stones by reducing the oxidative damage. Key words: Calcium oxalate; Epigallocatechin gallate; Oxidative damage