Fig. 3.

Circadian rhythm of DNA replication in mouse tissues. SKH-1 hairless mice were kept under an LD 12:12 cycle. BrdU or vehicle alone (“mock”) was injected intraperitoneally at either ZT 21 (4:00 AM) or ZT 09 (4:00 PM); 90 min later epidermis, intestine, and kidney tissues were harvested and the level of DNA replication was examined by slot blot. (A and B) Results obtained with wild-type SKH-1 hairless mice. (A) Representative slot blot. (B) Quantitative analysis of slot blots. Error bars indicate means ± SD (n = 3 mice at each time point). (C and D) Results obtained with clock-deficient (Cry1^−/−Cry2^−/−) mice. (C) Representative slot blot. (D) Quantitative analysis of the slot blots. Error bars indicate means ± SD (n = 3 mice at each time point).