MULTIPLE SUBSTRATE DETERMINATION OF MONOAMINE OXIDASE DISTRIBUTION AND IPRONIAZID INHIBITION IN RAT BRAIN¹

Abstract

Abstract— —A variety of monoamine oxidase substrates (tyramine, dopamine, serotonin, tryptamine) have been used with and without Iproniazid inhibition to evaluate further the extent to which enzyme multiplicity may exist in various regions of rat brain. Levels of monoamine oxidase activity, as measured by ammonia production, were found to vary as a function of both brain area and kind of substrate used, in the absence as well as in the presence of Iproniazid, in vivo and in vitro. Similarity of substrate metabolizing patterns among the different brain areas, however, strongly suggests that only one kind of monoamine oxidase exists in rat brain.

Multiple forms of rat brain mitochondrial monoamine oxidase. Subcellular localization

“…130% (5) and protein rec. 95%(6).according to Kornberg [ 131. MAO activities were determined by modifications of the methods used by Kraml [ 141, McCaman et al [ 151 and Neidle et al…”

“…MAO in rat brain appears to occur in multiple forms, which differ in substrate specificity [ 1] , inhibitor sensitivity [2], and electrophoretic mobility [3,4]. Whereas Kim and D'Iorio [S] , La Motte et al [6], and Hidaka et al [7] express a certain reserve with respect to this multiplicity of MAO, Youdim et al [3] , and Collins et al [8] believe that the multiple forms, obtained after solubilization and electrophoresis are genuine constituents of mitochondria and that their substrate preferences in vitro reflect their function in vivo.…”

Homovanillic and 5-Hydroxyindeleacetic Acids in Cerebrospinal Fluid After Probenecid: Measurement of Brain Monoamine Oxidase Inhibition in Vivo

“…In addition, the existence of more than one kind of monamine oxidase (MAO) in brain has been suggested (2)(3)(4) and disputed (5). Finally, only a small fraction of the total MA0 in heart and other tissues is localized in sympathetic nerve endings (6, 7) and it has been suggested that this fraction is partly localized in NEcontaining vesicles (8,9).…”