Ornithine decarboxylase in the organs of rats exposed to chronic low-dose γ-irradiation

Chronic exposure of rats to γ-irradiation at the dose rates of 1.1, 2.1 and 12.9 cGy/d in the dose ranges of 9-165, 17-315 and 100-2000 cGy, respectively, modified the ornithine decarboxylase (ODC)activity in the radiosensitive (thymus, spleen) and radioresistant (lung) organs. A nonmonotonic dependence of the ODC activity on the cumulative radiation doses was observed: a decrease in the ODC activity caused by low cumulative radiation doses (after 8 days of exposure) gave way to the level that was close to the control (after 45 and 90 days); after 150 days of exposure, the activity of ODC increased in some organs (spleen and lung). It was suggested that this nonmonotonicity has its origins in the radiation triggering the regulatory systems of the cell homeostasis. 15 refs., 3 figs