Determination of the optimal conditions to study DNA synthesis in cultures of mouse hepatocytes.

Mouse hepatocytes undergo profound changes during aging, such as increased nuclear volume, occurrence of tetraploid nuclei and impaired DNA synthesis following in vivo adrenergic stimulation. These alterations have been found reversible by implanting a neonatal thymus into old animals. In the present paper we studied the optimal experimental conditions in order to investigate the mechanisms of such actions in vitro. Unfortunately, in fact, most of data in the field comes from experiments on rats. Thus, we examined DNA synthesis of hepatocytes from mice cultivated in presence of neonatal calf serum only, or after the addition of the beta-adrenergic agonist isoproterenol or the beta-adrenergic antagonist propranolol. DNA synthesis in hepatocytes from young Balb/c-nu mice shows a peak between 36 and 48 h even in the absence of any specific stimulation other than newborn calf serum. The addition of isoproterenol does not modify the DNA synthetic pattern, while propranolol causes a slight but statistically significant decrease in 3H-thymidine incorporation. Results are compared with those obtained from other authors in rats.