title: Effect of bilirubin on the spectrophotometric and radionuclide assay for serum angiotensin-converting enzyme.
abstract: The effect of bilirubin on serum angiotensin-converting enzyme (ACE) activity was studied with spectrophotometric and radionuclide assays. In the spectrophotometric assay addition of bilirubin to normal serum from dog, mouse, and human produced a dose-related inhibition of ACE activity. A 50% decrease in human ACE activity was produced by the addition of approximately 250 mg/L in vitro. Serum from icteric patients with elevated bilirubin was also associated with a reduction in ACE activity in the spectrophotometric assay. A 50% decrease in ACE activity in these samples was associated with a serum bilirubin of approximately 220 mg/L. In the radionuclide assay, however, addition of bilirubin to normal human serum failed to reduce measured ACE activity. The use of a radionuclide assay for serum ACE in clinical samples offers the advantage of less interference from serum bilirubin.
mesh_terms: D000806:Angiotensin-Converting Enzyme Inhibitors; D000818:Animals; D001663:Bilirubin / Q000097:blood*; D004285:Dogs; D006801:Humans; D007565:Jaundice / Q000097:blood; D051379:Mice; D007703:Peptidyl-Dipeptidase A / Q000097:blood*; D011868:Radioisotopes; D013053:Spectrophotometry
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D011868:Radioisotopes; D007703:Peptidyl-Dipeptidase A; D001663:Bilirubin