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J Endourol. 2006 May;20(5):356-61.

Effects of green tea on urinary stone formation: an in vivo and in vitro study.

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1
Department of Urology, Seoul National University College of Medicine and Clinical Research Institute, Seoul National University Hospital, Seoul, Korea.

Abstract

PURPOSE:

We evaluated whether epigallocatechin gallate (EGCG), a main constituent of green tea polyphenols, could protect against cellular toxicity by oxalate and whether green tea supplementation attenuates the development of nephrolithiasis in an animal model.

MATERIALS AND METHODS:

Cells of the NRK-52E line were incubated with different concentrations of oxalate with and without EGCG, and toxicity and malondialdehyde assays were done to investigate the cytotoxic effect of oxalate and the anti-oxalate effect of EGCG.. In a second series of experiments, male Sprague-Dawley rats were divided into three groups. Group 1 animals (controls) were fed regular chow and drank water ad libitum; group 2 animals were fed chow containing 3% sodium oxalate with the administration of gentamicin (40 mg/kg) and drank water ad libitum; group 3 animals were fed the same diet as group 2 with gentamicin administration and drank only green tea. Rats were killed 4 weeks later after a 24-hour urine collection, and the kidneys were removed for morphologic examination.

RESULTS:

As oxalate concentrations increased, the number of surviving cells decreased, and the formation of free radicals increased. The administration of EGCG inhibited free-radical production induced by oxalate. Green tea supplementation decreased the excretion of urinary oxalate and the activities of urinary gammaglutamyltranspeptidase and N-acetylglucosaminidase. The number of crystals within kidneys in group 3 was significantly lower than in group 2.

CONCLUSIONS:

Green tea has an inhibitory effect on urinary stone formation, and the antioxidative action of EGCG is considered to be involved.

PMID:
16724910
DOI:
10.1089/end.2006.20.356
[Indexed for MEDLINE]
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