SummaryThe metabolism of arachidonic acid (AA), eicosapenta enoic 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 retro converted 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.

Effects of sesamin and curcumin on ‡™5-desaturation and chain elongation of polyunsaturated fatty acid (PUFA) were studied in rat primary cultured hepatocytes. When sesamin was added to culture medium containing 20:4 (n-3), rat hepatocytes after 24h of incubation Y. FUJIYAMA-FUJIWARA et al. sesamin into diets decreased the plasma level of cholesterol in rats (7) and changed the fatty acid composition in liver phospholipids probably by the decrease of ‡™5-desaturase activity (8). Also it has been reported that curcumin, a yellow pigment of turmeric used in curry powder, inhibited the ‡™5-desaturase of M. alpina (9) and increased the content of ƒÁ-linolenic acid in this mould oil. These results suggest that some food constituents may affect the metabolism of