MECHANISMS OF DOPAMINE AND DOBUTAMINE INTERFERENCE IN BIOCHEMICAL TESTS THAT USE PEROXIDE AND PEROXIDASE TO GENERATE CHROMOPHORE

Dopamine and dobutamine have recently been shown to produce a negative interference in several biochemical tests that use peroxide and perox idase to generate a chromophore. To define the chemical mechanism of t his interference, we examined the effects of dopamine and dobutamine i n various peroxidase-based biochemical tests. Dopamine interfered stoi chiometrically with peroxidase-based tests that use 4-aminophenazone t o form chromophore but interfered little in those that use other compo unds to generate chromophore. Dopamine reacts with 4-aminophenazone in the presence of peroxide and peroxidase to form a novel quinone-imine dye, with a smaller absorptivity than the chromophore formed in the a bsence of dopamine. The smaller absorptivity of this novel chromophore results in negative interference by reducing the total absorbance at the wavelength used to measure analyte. In contrast, dobutamine interf ered stoichiometrically with all peroxidase-based tests studied, regar dless of whether 4-aminophenazone was used to form the chromophore. Do butamine was rapidly oxidized by peroxide in the presence of peroxidas e, thus depleting the peroxide necessary to generate chromophore. Dopa mine and dobutamine demonstrate two distinct general mechanisms of int erference in peroxidase-based biochemical tests.