THE INFLUENCE OF DIETARY LIPIDS ON THE COMPOSITION AND MEMBRANE FLUIDITY OF RAT HEPATOCYTE PLASMA-MEMBRANE

Weanling male Wistar rats were fed for five weeks on standard rat chow (23 g fat/kg diet) or one of four synthetic diets with butterfat, coc onut oil, corn oil, or fish oil as the main lipid source (100 g fat/kg diet). In all diets, 10% of the fat was provided as corn oil to preve nt essential fatty acid deficiency. Significant differences were obser ved in the saturated, monounsaturated, and polyunsaturated fatty acid composition, and in the ratio of cholesterol to phospholipid, in the h epatocyte membranes. The fluidity of hepatocyte plasma membranes was a ssessed using the fluorescence recovery after photobleaching technique and steady-state fluorescence anisotropy of diphenylhexatriene. No si gnificant differences were found in the fluidity of plasma membranes b etween animals on the different fat diets, despite diet-induced change s in their fatty acid composition. However, the proportion of lipid fr ee to diffuse in the plasma membrane varied with diet, being significa ntly greater (P < 0.05) in animals fed chow (63.7%), coconut oil (61.5 %), and butterfat (57.6%) diets than in those fed the corn oil (47.3%) diet. Animals fed fish oil showed an intermediate (50.0%) proportion of lipid free to diffuse. The data support the hypothesis that dietary lipids can change both the chemical composition and lateral organizat ion (lipid domain structure) of rat hepatocyte plasma membranes.