Metabolism of arachidonic, eicosapentaenoic, and docosahexaenoic acids in HepG2 cells and rat hepatocytes.

The metabolism of arachidonic acid (AA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) was examined in HepG2 cells, a human hepatoma cell line, and rat hepatocytes. The AA level in HepG2 cells was lower than in rat hepatocytes and incorporation of AA into HepG2 was also smaller than into rat hepatocytes. Both cells could not increase the level of cellular DHA by the addition of exogenous 22:5 (n-3); whereas, rat hepatocytes, but not HepG2 cells, increased the levels of AA from 20:3 (n-6) and EPA from 20:4 (n-3). In both cells, retroconversion of AA to 20:3 (n-6) occurred, but EPA was not retroconverted to 20:4 (n-3). These results suggested that the levels of AA and DHA in both types of cells, were regulated more severely than EPA and that the activity of fatty acid desaturation might be different between n-6 and n-3 families.