Effects of γ-irradiation on isolated rat liver mitochondria

Gamma-irradiation of isolated rat liver mitochondria with up to 475 Gy leading to hydrated electrons (G = 1.9, corrected for reaction with solutes), 30 Gy leading to carbohydrate radicals, (G = 5.6), 100 Gy leading to superoxide radicals (G = 6.2), and 130 Gy leading to formate radicals (G = 6.2) showed no effects on the rate of oxygen uptake in various respiratory states, the respiratory control ratio, or the adenosine diphosphate to atomic oxygen ratio. Typical values were 0.020-0.100 nmol O2 s-1 mg protein-1 for State 1 respiration, 0.25-0.33 nmol O2 s-1 mg protein-1 for State 4 respiration and 0.65-1.10 nmol O2 s-1 mg protein-1 for State 3 respiration. Typical respiratory control ratios ranged from 2.0-3.5 for succinate and 4.0-6.5 for a 1:1 glutamate: malate substrate mixture. Adenosine diphosphate to atomic oxygen ratios with succinate as substrate varied from 1.6 to 1.9. In situ and in vitro irradiated mitochondria were examined by electron microscope and compared to mitochondria in situ, non-irradiated mitochondria and mitochondria isolated after whole liver irradiation. Irradiation of isolated mitochondria with 375 Gy results in partial destruction of the mitochondrial outer membrane with no significant changes in respiratory rates. (author)