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The effects of linoleic acid(LA, 18 : 2) and/or bovine serum albumin(BSA) on the lipid metabolism in human hepatoma cell line HepG2 cells were evaluated. HepG2 cells were cultured in basal Dulbecco´s modified Eagle´s(DME) medium(Basal medium), DME medium containing 0.2 mM LA(LA medium), or DME medium containing both 0.2 mM LA and 0.2-1.0% BSA(LA+BSA medium). [^(14)C]Acetate(0.3 μCi/㎖ medium) was added as a radioactive lipid precursor and the cells were incubated for 6 hours. An addition of LA to basal medium resulted in a decrease in the incorporation of [^(14)C]acetate into total cholesterol fraction. In contrast, an addition of BSA to LA-containing medium tended to increase the incorporation of [^(14)C]acetate into total cholesterol. The alteration of cholesterol metabolism in HepG2 cells incubated in LA+BSA medium was attributed by an increase in the incorporation of [^(14)C]acetate into free cholesterol, but not cholesteryl ester fraction. In addition, the secretion of cholesterol was increased by LA+BSA medium, suggesting that BSA stimulates cholesterol secretion. No significant change in the incorporation of [^(14)C]acetate into cellular total lipids was observed among the experimental groups. However, an increased incorporation of [^(14)C]-labelled fatty acid into cellular triacylglycerol and decreased incorporation into phospholipid were observed in cells incubated with LA+BSA medium as compared to those of LA medium. The secretions of [^(14)C]-labelled triacylglycerol, phospholipid, and free fatty acid were also stimulated in HepG2 cells incubated with LA+BSA medium. In conclusion, the present study suggests that in human hepatocytes, LA and BSA influence lipid metabolism, and BSA enhances the secretion of lipids.
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