Description
Introduction: Low-density lipoprotein (LDL) is a type of lipoprotein that transports cholesterol and triglycerides from the liver to peripheral tissues. LDL is one of the five major groups of lipoproteins; these groups include chylomicrons, very low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), low-density lipoprotein, and high-density lipoprotein (HDL), although some alternative organizational schemes have been proposed. Like all lipoproteins, LDL enables fats and cholesterol to move within the water-based solution of the blood stream. LDL also regulates cholesterol synthesis at these sites. It is used medically as part of a cholesterol blood test, and since high levels of LDL cholesterol can signal medical problems like cardiovascular disease, it is sometimes called "bad cholesterol". Oxidized LDL (Ox-LDL) is a form of LDL that has been bombarded with oxygen to yield free radicals when it enters into the wall of an artery. Once within the arterial wall, oxidized LDL promotes atherosclerosis by attracting other cells and chemicals to the site, causing inflammation at the site of the artery, and laying the foundation for cholesterol and other fats to build up within the artery. Under the oxidative stress, Ox-LDL may take place in the subendothelial space of the arterial wall, and a small amount of Ox-LDL may also be released into the circulation. When "fully oxidized LDL" enters the circulation in minor quantities, it will be rapidly cleared by the reticuloendothelial system, particularly in the liver, or it will be removed by the preexisting circulating autoantibodies to Ox-LDL. In contrast, the "minimally modified LDL," in which oxidative modification has not been sufficient to cause changes recognized by scavenger receptors, can be found in circulation.
Principle of the Assay: The microtiter plate provided in this kit has been pre-coated with an antibody specific to Ox-LDL. Standards or samples are then added to the appropriate microtiter plate wells with a biotin-conjugated antibody preparation specific for Ox-LDL and Avidin conjugated to Horseradish Peroxidase (HRP) is added to each microplate well and incubated. Then a TMB (3,3',5,5' tetramethyl-benzidine) substrate solution is added to each well. Only those wells that contain Ox-LDL, biotin-conjugated antibody and enzyme-conjugated Avidin will exhibit a change in color. The enzyme-substrate reaction is terminated by the addition of a sulphuric acid solution and the color change is measured spectrophotometrically at a wavelength of 450 nm +/- 2 nm. The concentration of Ox-LDL in the samples is then determined by comparing the O.D. of the samples to the standard curve