EVALUATION OF 3 METHODS FOR THE MEASUREMENT OF DIAMINE OXIDASE (DAO) ACTIVITY IN AMNIOTIC-FLUID

The activity of diamine oxidase (DAO) in amniotic fluid was measured by three different methods. The first two, one colorimetric and the other fluorometric, depended on the coupled peroxidase assay. The other was a radiochemical procedure. The latter proved to be a reliable method, free from interference and linear over a wide range of time and substrate concentration. The coupled peroxidase assay was shown to be affected by a variety of factors. It was not linear with time, owing to a lag period that varied from sample to sample. The hydrogen peroxide-peroxidase reaction was inhibited by high substrate concentrations and by undialyzed amniotic fluid. © 1979.