X-ray microanalysis of monovalent electrolyte contents of quiescent, proliferating as well as tumor rat hepatocytes.

Energy-dispersive X-ray microanalysis was carried out on normal and regenerating liver as well as on 3924 A hepatoma cells. Specimens were quickly removed from the sacrificed animals, frozen in liquid isopentane, fractured still in the frozen state and freeze-dried under vacuum. The dried samples were examined in secondary electron image mode, and the X-ray spectra were recorded by means of an EDAX 707A system. Sodium and chlorine contents were higher both in nuclei and cytoplasms of regenerating and tumor hepatocytes than in normal liver. Moreover, hepatoma cells showed higher sodium and chlorine contents than did normal proliferating hepatocytes. Potassium contents did not show any differences among the experimental models. The increased sodium content and the resulting increased Na:K ratios of proliferating normal and tumor cells were not due to a generalized increase of these parameters in all the cells, but to the presence of new cell populations with high Na content and high Na:K ratios. Findings of present work are consistent with the hypothesis that high sodium content is associated with mitogenesis. Moreover, the much higher concentration of sodium in tumor cells as compared with normal proliferating hepatocytes supports the hypothesis that the concentration of this ion is related to oncogenesis of hepatocytes.