[Cell population mechanisms of the diurnal rhythm of mouse hepatocyte mitotic activity]

The dynamics of 3H-thymidine labeled mitosis and diurnal rhythm of mitotic activity was studied. The isotope was injected to BALB/c male mice at the peak of diurnal rhythm of DNA synthetic activity of hepatocytes. It has been established that the increase in the mitotic index during 24 hours depends on the increase in number of cells being in S-period. On the 2nd and 3rd days of investigation no labeled dividing hepatocytes were observed at the phases of increased mitotic index. The data allow to conclude that the increase of mitotic index at diurnal rhythm is at the expense of new GO-cells which entered the mitotic cycle, rather than due to the re-entering of cells that had divided during the maximal mitotic activity the day before.