Changes in liver cells ploidy of young rats following isoprenaline treatment.

Cell proliferation induced by isoprenaline (IPR) stimulation in very high doses was assayed in the liver of young rats, and the formation of polyploid cells was studied form the 15th to the 70th day of life. A general stimulatory effect on a complex process of cellular multiplication, leading to a population of tetraploid cells, was found to be accelerated; the earlier appearance of binucleate cells and the subsequent significant variations in their incidence confirmed the role of this cell type as an intermediate step in the process of polyploidization. Evidence was found of concomitant size changes of the hepatocytes, which might be partially independent of the effect of DNA content. The stimulation was no longer evident 20--30 days from the end of treatment, by when the cells which had come into contact with IPR should have completed the whole sequence of events leading to the formation of tetraploid mononucleate cells.