The effects of fatty acids and antioxidants in the culture medium on membrane composition and properties of the microsomal enzymes aryl hydrocarbon hydroxylase and cytochrome c reductase of cultured liver cells.

Rat liver epithelial cells grown in medium without serum show characteristic changes in fatty acid composition and decreased levels of activity of the microsomal enzyme function aryl hydrocarbon hydroxylase. Manipulation of cell fatty acid composition was performed using albumin-fatty acid complexes. Both GLC analysis of fatty acid methyl esters and Arrhenius plots of enzyme activity indicate changes in membrane lipid composition without major changes in aryl hydrocarbon hydroxylase enzyme activity or inducibility by benzanthracene in the presence of butylated hydroxytoluene. When essential fatty acids were added without antioxidant, increased aryl hydrocarbon hydroxylase activity was found. These changes in microsomal aryl hydrocarbon hydroxylase activity were independent of changes in cytochrome c reductase. It is concluded that expression and induction of aryl hydrocarbon hydroxylase is not dependent upon cell fatty acid composition but may be enhanced under conditions of limited lipid peroxidation.