Recent data suggest that elevated serum semicarbazide-sensitive amine oxidase activity
(SSAO) may cause endothelial injury. Formation of cytotoxic metabolites (especially
formaldehyde) and increased oxidative stress might lead to initiation or progression
of atherosclerosis. Effective and selective inhibitors of human SSAO might exert cytoprotective
effect on endothelial cells. To compare the inhibitor sensitivity of human serum and
vascular tissue SSAO enzyme, the inhibitory effect of semicarbazide and MDL 72974A
was investigated. Serum and vascular SSAO activity has been determined using 14C-benzylamine
as a substrate. The IC50 values of semicarbazide were estimated to be 5x10-3M
and 5x10-4M for SSAO from human serum and saphenous vein, respectively.
MDL 72974A amine oxidase inhibitor was more than thousand times more effective than
semicarbazide. The IC50 values were 10-7M and 10-8M
for SSAO from human serum and saphenous vein, respectively. This finding supports
the hypothesis that soluble and membrane-bound vascular SSAO enzymes might have similar
structure.
