The radiosensitivity of human hepatocytes was determined and compared to that of rat hepatocytes. This interspecies comparison was performed by using the alkaline elution technique to measure DNA single-strand breaks and their repair in irradiated primary cultures of hepatocytes. Human hepatocytes obtained from discarded surgical material and Fischer 344 female rat hepatocytes were enzymatically dispersed with collagenase, placed in culture, and irradiated with 0, 10, 20, and 40 Gy of60 Co γ rays. The DNA was eluted either immediately after irradiation or at different times following incubation at 37°C to allow for DNA single-strand break repair. The slopes of the dose-response relationship (strand scission factor versus dose) without DNA repair were 0.014 ± 0.002 <tex-math>${\rm Gy^{-1}}$</tex-math> (n = 5) and 0.018 ± 0.003 <tex-math>${\rm Gy^{-1}}$</tex-math> (n = 12) in human and rat hepatocytes, respectively; they were not significantly different. The half-time for fast and slow repair in human and rat hepatocytes was also not significantly different (i.e., 17.8 ± 4.4 min and 253 ± 67 min, and 13.9 ± 6.1 min and 121 ± 31 min, respectively), and 15 to 25% of the initial radiation-induced DNA damage was still present after 3 h of repair.

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