The time-course of mouse liver regeneration after carbon tetrachloride injury is influenced by circadian rhythms.

Male NM mice received 50 nmol CC14 i.p. at 1800, 2400, 0600 or 1200 and the changes in regenerative DNA synthesis (incorporation of 3H-thymidine into DNA and labelling index) and mitotic rate were determined. The time-course of regeneration varied with the time of CC14 injection; when CC14 was injected at 0600 or 1200 biphasic patterns were observed, and when CC14 was injected at 2400 or 1800 single wide peaks were seen. Independently of time of CC14 injection, the DNA synthesis peaked at 2400, the acrophase of the circadian rhythm. Consequent to the DNA synthesis peaks, a similar pattern, 6 hr delayed, was observed for the mitotic rate values. The most pronounced synchronization was seen with CC14 injected at 1200.