CIRCADIAN-RHYTHMS OF KINETICS OF MOUSE ESOPHAGEAL EPITHELIAL-CELLS

The circadian rhythm of cell division and DNA synthesis and parameters of the mitotic cell cycle during the maximum and minimum of proliferation in the course of the 24-h period were studied in the epithelium of the mouse esophagus. The number of mitoses and DNA-synthesizing cells increased regularly at 1-7 a.m. and 10 p.m. -4 a.m. respectively. When [3H]-thymidine was injected into the mice at 2 a.m. the duration of the periods of the mitotic cycle was as follows: G2 min=1 h, G2+1/2M=2 h, S=7.1 h, and G1+1/2M=15.9 h. When [3H]-thymidine was injected at 2 p.m. the duration of the S-period was increased to 8.2 h, and that of G1+1/2M to 14.8 h. The total duration of the mitotic cycle in both series of experiments was 25 h. The duration of the individual phases of the mitotic cycle thus depends on the time of day and correlates with rhythmic changes in the number of dividing and DNA-synthesizing cells. The duration of the mitotic cycle is the same for cells passing through it at different times of day and is approximately the same as the period of the circadian rhythm of mitosis and DNA synthesis in the esophageal epithelium. © 1980 Plenum Publishing Corporation.