Role of a brush border membrane fatty acid binding protein in oleic acid uptake into rat and rabbit jejunal brush border membrane.

Oleic acid uptake was studied using adult rat and rabbit jejunal brush border membrane vesicles. The intestinal uptake of oleic acid is influenced by the activity of an amiloride-inhibitable brush border membrane Na+/H+ exchanger, NHE3: opposing Na+/H+ gradients (inward Na+ and outward H+ gradients) increased oleic acid uptake by about 40%, as compared with only an inward Na+ gradient, only an outward H+ gradient, or the absence of either Na+ or H+ gradients. This study was undertaken to test the hypothesis that a portion of oleic acid uptake is facilitated by a fatty acid binding protein in the brush border membrane (FABPPM) of adult rat jejunum. There was a reduction in the uptake of oleic acid when brush border membrane vesicles were incubated with a rat liver plasma membrane fatty acid binding protein antibody (anti-FABPPM-Ab) in the absence, but not in the presence, of opposing Na+/H+ gradients. Thus, oleic acid uptake occurs largely by partitioning of the lipid into the brush border membrane, as well as by a process which involves the activation of the brush border membrane Na+/H+ exchanger, and a membrane fatty acid binding protein.