ON THE ROLE OF HEPATIC CELL PLOIDY IN CHANGES IN LIVER FUNCTION WITH AGE AND FOLLOWING PARTIAL HEPATECTOMY

The ploidy state of liver parenchymal cells, and liver function in vivo, were measured with age. Liver function was determined using the bromsulphalein (BSP) retention test. Between 3 and 12 months there is an increase in BSP retention in the serum which parallels the polyploidy of the cells. After 12 months there was no change with age with respect to these parameters up to 27 months. After partial hepatectomy the BSP retention of rats younger than 12 months returned to control levels within 2 or 3 months, whereas the values in the older rats became the same as the values of the untreated rats within 3 weeks. This phenomenon might be explained by the fact that after partial hepatectomy there was a shift to polyploidy of the cells for rats younger than 12 months, but the ploidy state of the cells of the older rats did not differ after partial hepatectomy. It might be concluded that BSP retention is correlated with the ploidy state of the parenchymal cells. Great changes in liver function and ploidy state occurred in the first year of life. However, between 12 and 27 months neither parameter changed. Therefore, the rat liver seems to show little senile degeneration. Its capacity for regenerative growth is consistent with this conclusion.