A radioassay for angiotensin converting enzyme

Kenneth W. Ryder, Hannis Thompson, Daniel Smith, Martha Sample, Richard B. Sample, Tjien O. Oei

Research output: Contribution to journalArticle

5 Scopus citations


Current methods for measuring angiotensin converting enzyme activity (EC, ACE) are somewhat cumbersome and have limited the general availability of the test. We describe here a simple four-step radioassay for ACE which uses the substrate 14C-Hippurate-l-Histidyl-l-Leucine and measures the product, 14C-Hippurate. We found that incubation at pH 7.0 (Hepes buffer) increased the sensitivity of the test by 50 percent when compared to results obtained with the pH 8.0 buffer normally used for ACE assays. A split sample comparison study between the radioassay and the spectrophotometric method showed good correlation (n = 47; mean, spectrophotometric, 26.0 U/mL; mean, radioassay, 26.1 U/mL; m = 0.86; b = 3.9; r = 0.868). We found that there was no significant difference between the spectrophotometric, kinetic and radioassay (Newman-Keuls multiple range test), but the liquid chromatographic method gave results significantly different from the other methods. The assay for ACE described here combines enhanced technical ease with the sensitivity of a radioassay.

Original languageEnglish (US)
Pages (from-to)302-305
Number of pages4
JournalClinical Biochemistry
Issue number5
StatePublished - Oct 1984


  • angiotensin converting enzyme
  • enzyme tests
  • radioimmunoassay

ASJC Scopus subject areas

  • Clinical Biochemistry

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    Ryder, K. W., Thompson, H., Smith, D., Sample, M., Sample, R. B., & Oei, T. O. (1984). A radioassay for angiotensin converting enzyme. Clinical Biochemistry, 17(5), 302-305. https://doi.org/10.1016/S0009-9120(84)90601-5