[Age-associated increase in amount of DNA adducts in rat and human organs and its application to age estimation]

An age-associated increase of I-compounds, kinds of DNA adducts, was investigated in DNA extracts from various organs of rat and human for the possible application of it to the age estimation in legal medicine. Detection and relative quantitation of the I-compounds were made by 32P-postlabeling assay which is commonly used for analyzing DNA-adducts. In rats which were from 4 to 69 weeks old, the positive correlation was observed between age and relative I-compound level. A coefficient of correlation ranged from 0.906 to 0.435; the highest was that of the kidney and the lowest was that of the liver. Similar correlation was observed in the human aged from 18 to 79 years old (n = 22-24). A coefficient of correlation ranged from 0.700 to 0.415; the highest, the kidney and the lowest the liver, although coefficients of correlation in human were approximately 10-20% lower than those in rats. In spite of the fact that there were many considerable factors that affect to the amount of the I-compound, for example, various circumstances until death, diets, diseases and causes of death, those results in human encouraged us to estimate age from soft tissues. The regression lines of every organs obtained in this study (heart: Y = 44.018X + 28.527, standard error of estimate (S.E.) = 13.40, liver: Y = 88.099X + 23.833, S.E. = 13.76, kidney: Y = 218.029X + 3.263, S.E. = 12.14, brain: Y = 105.626X + 21.697, S.E. = 11.82, lung: Y = 36.838X + 26.891, S.E. = 12.94) enabled us to estimate age. The author found that this method was sufficiently useful even in comparison with previous methods for the age estimation from soft tissues.