Sodium/Hydrogen Exchanger 3 (NHE3) BioAssay™ ELISA Kit (Rat) is a Sandwich enzyme immunoassay. The microtiter plate provided in this kit has been pre-coated with an antibody specific to Sodium/Hydrogen Exchanger 3 (NHE3). Standards or samples are then added to the appropriate microtiter plate wells with a biotin-conjugated antibody specific to Sodium/Hydrogen Exchanger 3 (NHE3). Next, Avidin conjugated to Horseradish Peroxidase (HRP) is added to each microplate well and incubated. After TMB substrate solution is added, only those wells that contain Sodium/Hydrogen Exchanger 3 (NHE3), biotin-conjugated antibody and enzyme-conjugated Avidin will exhibit a change in color. The enzyme-substrate reaction is terminated by the addition of sulphuric acid solution and the color change is measured spectrophotometrically at a wavelength of 450nm±10nm. The concentration of Sodium/Hydrogen Exchanger 3 (NHE3) in the samples is then determined by comparing the O.D. of the samples to the standard curve.