Biochemical and Histochemical Studies of Liver Fatty Acid Binding Protein in Alcohol-Treated Rats.

Abstract

Liver fatty acid binding protein (L-FABP) is abundant in the cytosol, and is known to bind not only fatty acids but also several other endogenous and exogenous ligands. In order to determine the effects of alcohol on L-FABP synthesis and fatty acid metabolism, we studied the quantitative changes in fatty acid binding capacity (FABC) and immunoreactive L-FABP, and also the histochemical localization of L-FABP and triglycerides in the liver of rats given alcohol. Female SD rats in the control and in the two treated groups that were given 1g or 2g ethanol per kg body weight were fed the test solution of equal calories through a gastric tube every other day for 6 weeks. FABC determined by the 3H-labeled oleate binding assay and immunoreactive L-FABP measured by radioimmunoassay (RIA) increased in the treated groups (p<0.05 in FABC, p<0.005 in immunoreactive L-FABP). In the treated groups, the proportion of fatty acid-saturated L-FABP to total immunoreactive L-FABP was significantly increased in the rats fed 2g ethanol per body weight (p<0.05), and the difference of concentration of free fatty acids in the liver cytosol was not significant. In histochemical studies, L-FABP and neutral lipids were localized mainly in the cytoplasm of the periportal zone. When stained for both, the intensity and number of positive cells increased in the treated rats. These findings altogether indicated that ethanol increased fatty acid-saturated L-FABP and lipid deposition in the female rat liver, which suggests that L-FABP is involved in the mechanisms maintaining stable concentration of free fatty acids in the liver cytosol.