Effect of bilirubin on the spectrophotometric and radionuclide assay for serum angiotensin-converting enzyme
Saxe, A.W.; Hollinger, M.A.; Essam, T.
Research Communications in Chemical Pathology and Pharmacology 51(1): 129-136
1986
ISSN/ISBN: 0034-5164 PMID: 3006193 Document Number: 268392
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.