DIETARY-FAT EFFECTS ON BRUSH-BORDER MEMBRANE-COMPOSITION AND ENZYME-ACTIVITIES IN RAT INTESTINE

The effect of dietary fats on the chemical composition and enzyme acti vities has been studied in intestinal brush border membranes (BBM) of rats. Animals were given commercial rat pellet diet (RP) or semisynthe tic diet rich in either saturated [coconut oil (CCO)] or polyunsaturat ed [n-6, corn oil (GO) or n-3, fish oil (FO)] fat at the 10% level for 5 weeks. The membrane cholesterol/phospholipid ratio was augmented in CO- or RP-fed rats. There was an increase in level of saturated fatty acids in BBM from CCO- or FO-fed animals. n-3 polyunsaturated fatty a cid content was raised in FO-fed rats, while the proportion of linolei c acid and arachidonic acid was enhanced in animals given a CO diet. M embrane fluidity was in the order of CCO < RP = CO < FO. The membrane hexose content was high (p < 0.05) in the CCO group. Hexosamines were elevated (p < 0.05) in CCO- or FO-fed rat brush borders. Membrane fuco se was unaltered, while sialic acid content was elevated in CO- (p < 0 .05) and FO- (p < 0.01) fed vs. CCO-fed rats. Lectin binding to brush borders corroborated these findings. The activities of alkaline phosph atase, sucrase and lactase were augmented (p < 0.001) in CCO-fed anima ls. Leucine-aminopeptidase and sucrase activities were depressed by FO feeding. The activities of PNP-P-glycosidases were the highest in FO- fed rats. These results indicate that dietary fat quality markedly aff ects microvillus membrane lipid composition, glycosylation and enzyme functions in rat intestine.