[Circadian rhythm of hepatoma 22a cell division after exposure to liver chalone].

Chalone isolated from the cells of the normal rat liver exerts a pronounced inhibitory action on hepatoma 22a cell division during 9 hours after its administration. Then the mitotic activity of hepatoma cells returns to the control level, but after 15 hours it starts to diminish again. The total amount of cells that entered the mitotic cycle during the experiment declined by 30% as compared to the control. Thus, hepatic chalone produces a reversible inhibition of hepatoma cell division in G2 and G1 phases of the mitotic cycle and lessens the fraction of dividing cells over a period of 24 hours.