Tissue activity and cellular localization of human semicarbazide-sensitiveamine oxidase

Semicarbazide-sensitive amine oxidase (SSAO), widely distributed in highly vascularized mammalian tissues, metabolizes endogenous and xenobiotic aroma tic and aliphatic monoamines. To assess whether its physiological role in h umans is restricted to oxidation, we used an immunohistochemical approach t o examine the cellular localization of SSAO in human peripheral tissues (ad renal gland, duodenum, heart, kidney, lung, liver, pancreas, spleen, thyroi d gland, and blood vessels) and also analyzed its subcellular localization. The results are in agreement with the specific activities also determined in the same samples and are discussed with reference to the tissue distribu tion of monoamine oxidase A and B. Together with the oxidative deamination of monoamines, SSAO cellular localization indicates that, in most human per ipheral tissues, it might participate in the regulation of physiological pr ocesses via H2O2 generation.