ABSTRACT
This chapter describes the potential advantages of the use of stable isotope labeling in combination with chromatography, mass spectrometry, and stereospecific analysis of prefractionated intestinal lipoproteins and cellular membrane components as potentially unambiguous indicators of the absorption mechanism. Both analytical and preparative separations of lipid classes are necessary for studies of lipid digestion and absorption. Lipids exist in the intestinal lumen and mucosa in a variety of chemical and physical forms, including discrete droplets of neutral fat, mixed micelles, lipoproteins, and membranous vesicles, as well as monomeric molecules. Total lipid extracts are usually prepared by some variation of the chloroform-methanol routines originally described by J. Folch et al., E. G. Bligh and W. J. Dyer. Special precautions are necessary to minimize artifact formation during the extraction and purification of the total lipid extracts of intestinal mucosa. In the lower-phase lipids from rat mucosa, a constant pattern of five glycosphingolipid fractions could be distinguished, each chromatographed as a double band.
