D-AMINO-ACID IN IRRADIATED AND AGED MOUSE

A single high dose of X-rays (900R to the whole body or 1500R to the head alone) or gamma-rays (500R to the whole body) was applied to the mouse to promote the aging process, and the correlation of occurrence of D-amino acids to aging or cataract formation was examined in the skin and lenses. No D-amino acid was found in the skin even after irradiation. On the other hand, D-aspartic acid was detected in the insoluble fraction of lens protein from aged mice after irradiation. Irradiation simultaneously induced cataracts depending on the radiation dose. Thus, the irradiation promoted both the formation of cataract and D-aspartic acid in the lens protein, suggesting that the presence of D-aspartic acid in the lens might be considered as a molecular indicator of aging.