Electrophoretic analysis of lipoproteins

  • Electrophoretic analysis of lipoproteins

    LP plasma of blood - the transport form of lipids in the human body. They carry the transport of lipids as exogenous( food), and endogenous origin. Individual LPs capture excess cholesterol from cells of peripheral tissues to transport it to the liver, where it is oxidized to bile acids and excretion with bile. With the participation of LP are also transported fat-soluble vitamins and hormones.

    Plasma LPs have a spherical shape. Inside is a fat "drop" containing non-polar lipids( TG and esterified cholesterol) and forming the core of the LP particle. It is surrounded by a shell of phospholipids, unesterified cholesterol and protein.

    There are several methods for determining LP in the blood. One of them - the determination of the content of cholesterol in various classes of LPs - was considered above. Another method of studying the content of LP is electrophoretic. Using this method, individual LP fractions are classified by comparing their electrophoretic mobility with the mobility of conventional whey proteins. On the basis of electrophoretic mobility LP were divided into the following fractions.

    ■ Chylomicrons. When electrophoresis is performed, chylomicrons remain at the start( contain very little protein) like y-globulins;are fat-rich particles entering the blood from lymph and transporting food TG.They are the largest LPs. Plasma of blood of healthy people who did not take food for 12-14 hours, chylomicrons does not contain or contains them in insignificant amounts.

    ■ a-LP.With electrophoresis a-LP move together with a-globulins and correspond to HDL.HDL contains up to 50% protein, about 30% phospholipids, 20% XC and very little TG.Formed in the liver and small intestine wall.

    ■ p-LP.With electrophoresis on paper, the p-LP moves along with p-globulins and correspond to LDL.LDL contain 25% protein, 50% cholesterol, 20% phospholipids and 8-10% TG.It is suggested that LDL is formed partially or completely during the breakdown of very low density lipoproteins( VLDL).

    ■ Pre-R-LP.With electrophoresis, pre-R-LP are between a-LP and P-LP, they correspond to VLDL.

    LP electrophoresis allows a qualitative analysis of LP.There are two metabolic processes that determine the pathogenesis of atherosclerosis: the rate of infiltration of the rich cholesterol in the inner layer of the blood vessel wall and the rate of removal of cholesterol from the vessels with subsequent excretion from the body. In this balanced system, elevated concentrations of chylomicrons, VLDL and LDL determine the risk of excessive deposition of cholesterol within the vessel wall. On the other hand, increased HDL concentrations contribute to an increase in the rate of removal of cholesterol from atherosclerotic plaques. The LP electrophoresis method can provide additional information on the relationship of these metabolic processes.

    In addition to the above classes of LP, other LP-complexes, including unusual ones, which are called abnormal( or conditionally pathological) LP, can be found in the blood plasma. These include R-VLDLP, LPVPhs and LP-X.R-VLDL, also called P-LP floating, is characterized by the electrophoretic mobility inherent in P-LP and the density corresponding to VLDL, so that it floats up with ultracentrifugation along with the latter. The presence of R-VLDL is a characteristic feature of type III of DLP.LPVPxc is a fraction of HDL, overloaded with cholesterol, the role of these LP in the pathogenesis of atherosclerosis is not clear. LP-X is characterized by a high content of phospholipids( 65-68%) and non-esterified cholesterol( 23-27%).Due to their high rigidity, LP-X helps increase the viscosity of the blood. They appear in the blood with obstructive jaundice and in the absence of lecithin-cholesterol acyltransferase. The role of LP-X in the development of atherosclerosis has not been studied.