Secretion of plasma proteins and its insulin-dependent regulation in rat hepatocyte-hepatoma hybrid cells.

Hepatocyte-hepatoma hybrid cells were obtained by fusion of primary rat hepatocytes with Fao hepatoma cells. Synthesis and secretion of the liver-specific plasma proteins albumin and transferrin were preserved in these proliferating hybrids, called hepatocytoma cells. In the hybrid clone 1E3, secretion of albumin was 75% and that of transferrin was 45% of the secretion in normal hepatocytes. The level of albumin mRNA was fivefold higher in hepatocytoma cells than in normal hepatocytes. Essentially no albumin and transferrin secretion or albumin mRNA was found in the parental Fao hepatoma cells. Insulin decreased the albumin mRNA level in hybrid cells, while it increased the level in normal hepatocytes. This indicates an inverse effect of the hormone due to this regulation in immortalized hepatocytoma cells compared to normal hepatocytes.