Serum lipoprotein patterns in coronary sclerosis and associated conditions.

The association of coronary sclerosis with a disturbance of lipid metabolism is now fairly generally recognized. The cholesterol of the atherosclerotic plaque is derived, at least in part, from the circulating cholesterol (Biggs et al., 1952). At present the only objective measure of such a disturbance in the living subject is analysis of the circulating lipids. Previously it has been shown that there is significant elevation in subjects of coronary sclerosis compared with the normal of plasma total cholesterol and its ratio to the total circulating phospholipids, the C/P ratio (Gertler et al., 1950; Steiner et al., 1952; Oliver and Boyd, 1953b). There is evidence, which has been summarized by Russ et al. (1951), Nikkila (1953), and Swahn (1953), that the circulating lipids do not exist free in the plasma but are attached to protein. Cholesterol is associated with all the protein fractions but by far the greatest concentration is attached to the al and #I globulin fractions (Blix et al., 1941), thus these two lipid-laden globulin fractions are termed the a and : lipoproteins. It is obviously important to study the distribution of cholesterol between these two principal lipid carriers. An analytical approach towards the estimation of these complex colloidal lipoproteins was only made possible within recent years by the development of new physical methods. The low temperature chemical fractionation of plasma lipoproteins by the elaborate solubility procedure of Cohn et al. (1950), even at the micro level as developed by Russ et al. (1951), requires about 25 ml. of serum and considerable technical skill. The ultracentrifugal analytical flotation method, which has been so well developed by Gofman et al. (1950), for the examination of lipoprotein molecules, necessitates the possession of expensive and complex equipment. A third physical characteristic, the different rate of migration of the protein fractions in a buffer in an electric field, may be utilized for the separation of the lipoproteins by zone electrophoresis. This procedure has been applied with various modifications to the study of lipoproteins by Nikkila (1953), Swahn (1953), and Rosenberg et al. (1954). These authors support the suggestion of Barr et al. (1951), that the normal distribution of cholesterol between the two lipoprotein patterns is changed in the presence of coronary sclerosis and that the concentration of cholesterol on the ,B lipoprotein fraction is increased. The electrophoretic principle is attractive in its simplicity and was therefore employed in this study.