Radiation-induced inhibition of RNA synthesis in Tetrahymena pyriformis.

Radiation-induced disturbances in RNA synthesis were investigated in exponentially growing Tetrahymena. Sub-lethal doses of gamma-radiation lead to a transient, dose-dependent decrease in the rate of total RNA synthesis measured by 3H-uridine incorporation, without an alteration of 3H-uridine uptake by the cells. The rate of 3H-uridine incorporation decreases exponentially with dose. In contrast, the duration of inhibition of RNA synthesis is linearly dependent on dose. Target-theory calculations suggest that the sensitive molecule has a molecular weight of about 2 X 10(7) Daltons.