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RNA polymerase activities in liver and brain tissue of aging mice.

RNA polymerase activity has been measured in liver and brain of C57BL-6J mice to determine if a change in enzyme activity can be correlated with decreasing survivorship of the animals. The RNA polymerases in tissue homogenates were solubilized by treatment with a buffer of high ionic strength and resolved by DEAE-Sephadex chromatography. Enzyme activity was quantitated by measuring the incorporation of [3H]UMP into RNA using heat denatured calf thymus DNA as the template. Statistically significant differences in polymerase activities were not observed in liver tissue from 18-, 25-, and 29-month-old animals or in brain tissue from 23- to 31-month-old animals. These age groups span the period of most rapid decrease in survivors,ip in our colony of mice (from 93% to 16%). The evidence indicates that changes in liver or brain RNA polymerase activities are not correlated with the rapid decrease in survivorship of these animals.