An autoradiographic method of visualising semicarbazide-sensitive amine oxidase activity in mouse tissue sections

Under the influence of semicarbazide-sensitive amine oxidase (SSAO), methylamine is deaminated to formaldehyde, which can react with various macromolecules and form irreversible adducts. We hereby present an autoradiographic method of visualising SSAO activity by measuring the in vivo formation of such adducts from 14C-methylamine. Our results revealed high concentrations of radioactive deposits in the intestinal wall, brown adipose tissue, spleen and bone marrow. Hydralazine is a potent SSAO inhibitor and pretreatment with this irreversible inactivator resulted in a nearly complete loss of radioactive deposits in the tissues. By giving 14C-methylamine at different time-points after irreversible inhibition of SSAO, it was also possible to determine the resynthesis rate of SSAO. Interestingly, the recovery rate of SSAO after such inactivation was tissue-specific. The possible therapeutic value of a specific SSAO inhibitory drug has been discussed.