Indirect immunofluorescence techniques were employed to determine the distribution within intestinal epithelial cells of apolipoprotein B, a protein essential for the normal transport of fat. Isolated intestinal cells were prepared from rats either during active lipid absorption or after biliary diversion. Specific immunofluorescence from an antiserum to apolipoprotein B was detected in the apical portion of epithelial cells from bile-diverted animals, demonstrating that a pool of apolipoprotein B is present in the nonabsorptive epithelial cell and may be a component of intestinal cell membranes. During lipid absorption in normal rats, an early and sustained increase in immunofluorescence was demonstrated, consistent with an increase synthesis of apolipoprotein B during lipid absorption. This study demonstrates the presence of apolipoprotein B within intestinal epithelium and provides evidence for the participation of this apoprotein in intestinal lipid transport.

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