The Effect of Prior Continuous Irradiation on the G 2 , M, and S Phases of Proliferating Parenchymal Cells in the Regenerating Liver

Abstract

The pattern of parenchymal cell proliferation in the regenerating liver after partial hepatectomy was examined in 6- to 8-week-old August rats and C57BL mice by analyzing the percentage labeled mitoses curves after injection of tritiated thymidine. The curves indicated that for both species the approximate duration of the G2 + M/2 phase complex was 3.0 to 4.0 hr., and of the S phase, 8.0 hr. Since most cells divided only once, and only a few twice or more, the duration of the G1 phase and toe cycle time of the cells dividing for a second time could not be measured with any precision. Continuous whole-body [gamma]-irradiation at 47 rads/day for 15 days and 30 days to accumulated doses of up to 1400 rads prior to partial hepatectomy caused a greater variation and possibly a shortening of the duration of the G2 + M/2 period to 2.5 to 3.0 hours and a slight decrease in the duration of the S phase to 7.0 to 7.5 hr.