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


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.
Jeong
Byong Chang
BC
Department of Urology, Seoul National University College of Medicine and Clinical Research Institute, Seoul National University Hospital, Seoul, Korea.
Kim
Bong Sub
BS
Kim
Jung In
JI
Kim
Hyeon Hoe
HH
D000118:Acetylglucosaminidase / Q000652:urine; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology* / Q000633:toxicity; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000633:toxicity; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004848:Epithelium / Q000187:drug effects; D005609:Free Radicals / Q000378:metabolism; D066298:In Vitro Techniques; D007669:Kidney Calculi / Q000473:pathology / Q000517:prevention & control* / Q000652:urine; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D015227:Lipid Peroxidation; D008297:Male; D008315:Malondialdehyde / Q000494:pharmacology; D010070:Oxalates / Q000494:pharmacology / Q000633:toxicity / Q000652:urine; D051381:Rats; D017207:Rats, Sprague-Dawley; D013662:Tea; D005723:gamma-Glutamyltransferase / Q000652:urine
D000975:Antioxidants; D005609:Free Radicals; D010070:Oxalates; D013662:Tea; D008315:Malondialdehyde; D002392:Catechin; C045651:epigallocatechin gallate; D005723:gamma-Glutamyltransferase; D000118:Acetylglucosaminidase