Cell-density dependent expression of the c- [formula omitted] gene in primary cultured rat hepatocytes

Abstract

During culture of mature rat hepatocytes as monolayers, c- myc mRNA was found to be expressed transiently within 2 h, decreasing rapidly to the basal level at 10 h. Then its level increased again to over 10-fold the basal level at 24 h, and remained at this high level during culture. The increase of c- myc mRNA in the second phase was shown by nuclear run-off experiments to be due to an increase of its transcription. The second, but not the first, increase in c- myc expression was inversely proportional to the cell density in culture. The expression of c- myc mRNA was not affected by various hormones including growth factors. These results indicate that hepatocytes in culture at lower cell density tend to move from the G o phase to the G 1 phase, but remain in the G o phase when cultured at high cell density.