Abstract
We examined the protective effect of tea catechin against X-ray-induced chromosomal damage using the micronucleus assay. Male ICR mice were orally administered tea catechin extract at 10-300mg/kgBW/day for 7 days, then subjected to X-ray irradiation at 0.5 Gy. The resulting chromosomal damage to bone marrow was evaluated by the micronucleus assay using peripheral blood. Tea catechin extract tended to protect the bone marrow from X-ray-induced chromosomal damage. To examine this radioprotective effect of tea catechin in more detail, human lymphoblastoid WIL2-NS cells were incubated with various concentrations of (-) -epigallocatechin3-O-gallate (EGCg), the main constituent of tea catechins, and then exposed to 0.5 Gy of X-ray radiation. The resulting chromosomal damage was evaluated by a cytokinesis-block micronucleus assay. A high dose of EGCg (10μM) protected WIL2-NS cells from X-ray-induced chromosomal damage, but a physiological dose (<1μM) did not. EGCg was markedly decomposed by X-ray irradiation, indicating a direct reaction between EGCg and X-rays. These results suggest that although tea catechin has a radioprotective effect, no such effect can be expected at a physiological dose.
