Abstract
We studied radiation-induced mutations in a transgenic mouse, HITEC, which carries the rpsL gene as a reporter for mutations. We also performed a partial hepatectomy to induce cell proliferation and thereby increase the detection of mutations. HITEC mice were irradiated with 5 Gy of gamma rays before hepatectomy, and the remnant-regenerating liver was excised after hepatectomy. The mutation frequencies for both the resected liver at the partial hepatectomy and the remnant-regenerating liver were analyzed. We previously reported that in mice in which hepatectomy was performed 2 days after irradiation and the remnant liver was excised 3 days after hepatectomy, the mutation frequency was increased approximately twofold. In mice in which hepatectomy was performed 10 days after irradiation and the remnant liver was excised 3 or 10 days after hepatectomy, the mutation frequency was two to three times greater. These results indicated that partial hepatectomy increases the frequency of radiation-induced mutations, and that the mutations remained in the liver cells for at least 10 days after irradiation. In this study, the periods between irradiation and hepatectomy were set to 30 and 60 days and the remnant liver was excised 3 days after hepatectomy. We did not see an increased mutation frequency in either group. This result shows that the mutation repair system is obviously working even in terminally differentiated cells.
