Ultrastructural cytochemistry of p-N,N-dimethylamino-beta-phenethylamine (DAPA) oxidation reactions. "activation" and inhibition studies.

The oxidation of p-N,N-dimethylamino-beta-phenethylamine (DAPA) by amine oxidase(s) (AO), i.e., diamine oxidase (DAO), monoamine oxidase (MAO) and/or possibly other oxidases, has been previously demonstrated. This study reports the results of variations in fixation procedures and the incorporation of a series of possible "activators" and inhibitors into the DAPA oxidase (DAPAO) and DAPAO-BSPT [2-(2'-benzothiazolyl)-5-styryl-3-(4'-phthalhydrazidyl) tetrazolium chloride] reaction media in an attempt to elucidate the oxidase(s) involved. Results of these studies are indicative of at least two different oxidases acting preferentially on one or the other of the two systems. The presence of MAO, especially in unfixed tissue, and DAO, especially in fixed tissue, is denoted and that of other oxidase(s) is connoted.