Effect of ionizing radiation on liver mitochondrial respiratory functions in mice

Objective To investigate the radiation effect on mitochondria of the mouse liver in vivo. Methods Livers of BALB/c mice were squeezed out through openings cut on the upper abdomen and radiation doses were delivered only to the livers. Radia tion effects on the structure and function of liver mitochondria were evalu ated from both respiratory control ratio (RCR) and ADP/O (adenosine 5'-diph osphate/oxygen) ratio supported by two substrates, succinate and glutamate/ malate mixtures. Results The data showed that both state 3 and state 4 respiratory rates wer e significantly decreased concomitantly with the increase of radiation dose up to 20 Gy. Succinate-supported, but not glutamate/malate-supported, resp iratory control ratio, was also decreased with the increase of radiation do se. ADP/O ratios measured from the support of both succinate and glutamate/ malate were not changed by gamma-radiation. This differential radiation dam age indicated that respiratory control ratio was more radiation than oxidat ive phosphorylation. Conclusions Although the functional integrity of ATP synthetic machinery of the mitochondria was not perturbed by ionizing radiation under 20 Gy, the structural integrity of mitochondrial membrane might be affected by ionizin g radiation at a dose-dependent manner.