ELISA法定量测定人血清、血浆或其它相关液体中低密度脂蛋白(LDL)含量。

本试剂盒应用双抗体夹心酶标免疫分析法测定标本中LDL水平。用纯化的抗体包被微孔板，制成固相抗体，往包被单抗的微孔中依次加入LDL、生物素化的抗人LDL抗体、HRP标记的亲和素，经过彻底洗涤后用底物TMB显色。TMB在过氧化物酶的催化下转化成蓝色，并在酸的作用下转化成最终的黄色。颜色的深浅和样品中的LDL呈正相关。用酶标仪在450nm波长下测定吸光度（OD值），计算样品浓度。

This immunoassay kit allows for the specific measurement of human low density lipoprotein,LDL concentrations in cell culture supernates, serum, and plasma.

Low-density lipoprotein (LDL) belongs to the lipoprotein particle family. Its size is approx. 22 nm but since LDL particles contain a changing number of fatty acids they actually have a mass and size distribution. Each native LDL particle contains a single apolipoprotein B-100 molecule (Apo B-100, a protein with 4536 amino acid residues) that circles the fatty acids keeping them soluble in the aqueous environment.Generally, LDL transports cholesterol and triglycerides from the liver.

Because LDLs transport cholesterol to the arteries and can be retained there by arterial proteoglycans starting the formation of plaques, increased levels are associated with atherosclerosis, and thus heart attack, stroke and peripheral vascular disease. This is why cholesterol inside LDL lipoproteins is called bad cholesterol. Still, it is not the cholesterol that is bad; it is instead how and where it is being transported, and in what amounts over time.

Increasing evidence has revealed that the concentration and size of the LDL particles more powerfully relates to the degree of atherosclerosis progression than the concentration of cholesterol contained within all the LDL particles[citation needed] . The healthiest pattern, though relatively rare, is to have small numbers of large LDL particles and no small particles. Having small LDL particles, though common, is an unhealthy pattern; high concentrations of small LDL particles (even though potentially carrying the same total cholesterol content as a low concentration of large particles) correlates with much faster growth of atheroma, progression of atherosclerosis and earlier and more severe cardiovascular disease events and death.

LDL is formed as VLDL lipoproteins lose triglyceride through the action of lipoprotein lipase (LPL) and become smaller and denser, containing a higher proportion of cholesterol.

A hereditary form of high LDL is familial hypercholesterolemia (FH). Increased LDL is termed hyperlipoproteinemia type II (after the dated Fredrickson classification).

 

LDL poses a risk for cardiovascular disease when it invades the endothelium and becomes oxidized since the oxidized form is more easily retained by the proteoglycans. A complex set of biochemical reactions regulates the oxidation of LDL, chiefly stimulated by presence of free radicals in the endothelium. Nitric oxide down-regulates this oxidation process catalyzed by L-arginine. Correspondingly when there are high levels of asymmetric dimethylarginine in the endothelium, production of nitric oxide is inhibited and more LDL oxidation occurs.Test principle

This assay employs the quantitative sandwich enzyme immunoassay technique. A monoclonal antibody specific for LDL has been pre-coated onto a microplate. Standards and samples are pipetted into the wells and any LDL present is bound by the immobilized antibody. An enzyme-linked polyclonal antibody specific for LDL is added to the wells. Following a wash to remove any unbound antibody-enzyme reagent, a substrate solution is added to the wells and color develops in proportion to the amount of LDL bound in the initial step. The color development is stopped and the intensity of the color is measured.