Some histamine-related compounds interacting with the benzylamine-oxidizing activity of rat white adipocytes

In rat white adipocytes histamine is oxidized by a semicarbazide-sensitive amine oxidase which has benzylamine or preferential substrate (Bz-SSAO). To determine whether Bz-SSAO could control the extracellular levels of histamine and other histamine-related compounds active in lipid mobilization, a series of histaminergic compounds was screened as possible substrates or inhibitors of Bz-SSAO activity. Histaminergic compounds with imidazolo or thiazolo groups are oxidized by rat white-adipocyte Bz-SSAO whereas S-isothiourea derivatives, with two- or three-carbon-atom alkyl chains between the isothiourea and the N,N-dimethyl residue are, instead, inhibitors of the enzyme. Amtamine has been identified as a selective, high affinity substrate for rat white adipocyte Bz-SSAO. This enzymatic degradation might represent a catabolic pathway for the drug. These results show that the histaminase property of the rat white-adipocyte enzyme Bz-SSAO also extends to other histamine derivatives active at histamine receptors.