Mitotic Circadian Rhythm in a Fast-Growing and a Slow-Growing Hepatoma: Mitotic Rhythm in Hepatomas 2

A circadian rhythm is reported in the mitotic activity of a fast-growing hepatoma (SS1K) and a slow-growing hepatoma (SS1H). These tumors are 2 different sublines of a spontaneous hepatoma transplanted in 1949 by J. W. Wilson, Brown University, Providence, Rhode Island, into C3H/StWi strain. Significantly higher values in mitotic activity were observed during light periods than during dark periods. The SS1K hepatoma presented higher values than the SS1H hepatoma during the dark period, but the values for both hepatomas were not different during the light period. The variation was significantly higher in the slow-growing hepatoma and approached that of the immature liver.