Description
Introduction: Angiotensin causes blood vessels to constrict, and drives blood pressure up. It is part of the renin-angiotensin system, which is a major target for drugs that lower blood pressure. Angiotensin also stimulates the release of aldosterone from the adrenal cortex. Aldosterone promotes sodium retention in the distal nephron, which also drives blood pressure up. Angiotensin I is formed by the action of renin on angiotensinogen. Renin is produced in the kidneys in response to both decreased intra-renal blood pressure at the juxtaglomerular cells, or decreased delivery of Na+ and Cl- to the macula densa. If more Na+ is sensed, renin release is decreased. Renin cleaves the peptide bond between the leucine and valine residues on angiotensinogen, creating the ten amino acid peptide (des-Asp) angiotensin I. Angiotensin I appears to have no biological activity and exists solely as a precursor to angiotensin II. Angiotensin I is converted to angiotensin II through removal of two terminal residues by the enzyme Angiotensin-converting enzyme, which is found predominantly in the capillaries of the lung.
Principle of the Assay: The microtiter plate provided in this kit has been pre-coated with an antibody specific to Ang-I. Standards or samples are then added to the appropriate microtiter plate wells with a biotin-conjugated antibody preparation specific for Ang-Iand 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 Ang-I, 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 Ang-Iin the samples is then determined by comparing the O.D. of the samples to the standard curve