Low-Density Lipoprotein (LDL) Experimental Instructions for Use Purpose: This kit is used to determine the level of low-density lipoprotein (LDL) in rat serum, plasma, and related fluid samples. Principle of the experiment: This kit uses a double-antibody sandwich method to measure the rat's low-density lipoprotein (LDL) levels. The purified microtiter plate was coated with purified rat low-density lipoprotein (LDL) antibody to make a solid-phase antibody. The low-density lipoprotein (LDL) was added to the micro-wells of the coated monoclonal antibody, followed by the low density of HRP-labeled antibodies. The lipoprotein (LDL) antibody binds to form an antibody-antigen-enzyme-labeled antibody complex, and after thorough washing, the substrate TMB is developed. TMB is converted to blue under the catalysis of the HRP enzyme and converted to the final yellow color by the action of acid. The depth of color was positively correlated with rat LDL in the sample. The absorbance (OD value) was measured with a microplate reader at a wavelength of 450 nm, and the concentration of rat low-density lipoprotein (LDL) in the sample was calculated using a standard curve.