Background: Oxalate is a frequent component in foods from plant origin. Extraordinary concentrations of oxalate in urine leads to several renal pathological disorders. Green tea and black tea have several beneficial effects attributed to their polyphenols which act as metal chelators and scavengers of free radicals.  Aim: The present study aimed to clarify the possible ameliorating impact of black and green tea on renal tissue damage caused by oxalate.  Material and Methods: Thirty male mice were divided into six groups: Group I (control) ,Group II were injected with sodium oxalate, group IIIwere fed with black tea extract and group IV were fed with black tea extract and injected with sodium oxalate, group V were fed with green tea extract and group VI were fed with green tea extract and injected with sodium oxalate. The black or green tea extracts were given orally for 10 days (2ml/100g/day ). Sodium oxalate (100 mg/kg) were injected as a single intraperitoneal dose at the11th day and animals sacrificed 12 h later. At the end of experiment, blood samples and kidney specimenswere obtained from all groups. Serum urea and creatinine analysis were done. The renal tissue sections were stained with H&E and PAS stains and examined. Immunohistochemical investigation for iNOS and NF-κB and morphometric analysis were also implemented.  Results:Microscopically, the examined kidneys in oxalate group revealed degenerated and necrotic tubular cells ,tubular dilatation, protein casts and translucent oxalate crystals and interrupted tubular brush border and basal laminae. Furthermore, serum urea and creatinine were elevated and iNOS and NF-κB immunoreaction were highly positive. The aforementioned changes were reversed in group IVand VI.
Conclusion: Black and green tea extracts could protect against oxalate-induced nephrotoxicity due to their antioxidant characters.