ABSTRACT
The term lipid designates the class of compounds which are soluble in organic solvents and insoluble, or nearly so, in water. Serum lipids are carried in the aqueous circulation in the form of lipoproteins, in combination with certain proteins designated apolipoproteins. Recognition of the contribution of the lipids to the high prevalence of coronary heart disease in the developed countries has driven intense research into the epidemiology, mechanisms, pathology, and methodology over decades. Measurements of the apolipoproteins, other lipoprotein fractions, and other lipids are of interest primarily in specialty laboratories and for research studies. The wide range in density observed among the lipoprotein classes is a function of the relative lipid and protein content and enables fractionation by ultracentrifugation. Phospholipids are often measured in research, for example, in studies of dietary influences. Cholesterol and sometimes other lipids are quantitated in serum and in the fractions by enzymic or other assay methods.
