Effect of Green Tea on Calcium Oxalate Stone Formation and Excretion in Ethylene Glycol-treated Rats / 대한비뇨기과학회지

ABSTRACT

PURPOSE: To evaluate the therapeutic potential of green tea to treat renal stone, we examined the effect of green tea on the formation and the excretion of experimentally induced calcium oxalate (CaOx) stones in rat kidneys. MATERIALS AND METHODS: CaOx nephrolithiasis was induced by administering 1% ethylene glycol (EG) for 4 weeks. To investigate the effect of tea on the formation CaOx stones, the rats were simultaneously administered either 0.2% green tea or 0.5% rooibos tea. To verify the action of green tea on the excretion of CaOx stones, the rats were divided into four groups after the administration of 1% EG water for 4 weeks and then fed with either 0.2% green tea, 0.5% rooibos tea or 80mg/l furosemide-containing 1% EG water for 4 weeks. The right kidney was frozen for mRNA measurements, with the left fixed for counting crystal deposits. Twenty-four hour urine volume and urinary excretions of oxalate, uric acid, calcium and magnesium were measured. RESULTS: Urinary biochemistry and 24 hour urine output were apparently unchanged by taking either the green tea or rooibos tea. The increases of CaOx crystal deposits and osteopontin mRNA expressions in the kidneys by the administration of 1% EG water were markedly decreased by both tea intakes, while there were no significant differences in the mRNA levels of CuZn- and Mn-superoxide dismutases between the groups. CONCLUSIONS: Green and rooibos teas significantly attenuated the calcium crystal depositions in the kidneys. Down-regulations of the osteopontin mRNA levels may be involved in the inhibitory effects of the teas on the renal CaOx stone formation.