The time function of P32 incorporation in DNA of regenerating liver; the effect of irradiation.

Abstract

Following a massive dose of carbon tetrachloride in mice, a time study was made on the 2-hour incorporation of P32 into liver DNA and on the mitotic activity of liver cells. An increase in P32 incorporation began 30 hours after CCl4, with a maximum at about 40 hours. Mitotic activity was not apparent until after DNA synthesis had reached its maximum. The radiation experiments (with varying time intervals between CCl4, 800 r total-body x-radiation, and sacrifice) showed that DNA synthesis was depressed when the mice were irradiated 0, 12, 72, or 96 hours after administration of CCl4, but that it was not affected when the radiation was given between 24 and 48 hours after CCl4. Mitotic activity was absent 5 hours after radiation, began to return at 14 hours, and reached the control value at 26 hours. The results indicate that separate mechanisms are responsible for the effects of irradiation on DNA synthesis and on mitotic activity in liver.