Semicarbazide-sensitive amine oxidase (SSAO) from human and bovine cerebrovascular tissues: biochemical and immunohistological characterization

Semicarbazide-sensitive amine oxidase (SSAO) is widely distributed in almos t all tissues, especially in vascularized ones. However, its presence in br ain microvessels is still controversial. We have investigated the presence of SSAO in human and bovine brain microvessels by biochemical and immunohis tological techniques, and we have compared it with SSAO present in meninges from the same species. SSAO metabolizes benzylamine and methylamine in all tissues tested and possibly dopamine and octopamine as well, as shown in c ompetition studies. Kynuramine inhibited the metabolism of benzylamine by S SAO with high affinity in a noncompetitive manner. Western-blot analysis re ndered a positive staining of a 100 kDa band, in tissues from both species. These results were confirmed by immunohistological studies: the tunica med ia and intima of the meninges from both species were positively stained, an d so was the endothelial layer of microvessels. SSAO was absent in brain pa renchyma. These results definitively confirm the presence of SSAO in human and bovine cerebrovascular tissues and they demonstrate for the first time, the presence of this amine oxidase in endothelial cells from microvessels, through biochemical and immunological approaches. (C) 1998 Elsevier Scienc e Ltd. All rights reserved.