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In the mesenteric arterial bed of the rat the semicarbazide-sensitive amine oxidase with a high affinity for benzylamine (Bz. SSAO) (E.C. 1.4.3.6) is also able to oxidize histamine. In the perfused mesenteric arterial bed of the rat the complete inhibition of the Bz. SSAO obtained with a specific inhibitor, B24, almost completely reduces the efflux of imidazole acetic acid and increases the relaxing effect of histamine. Bz. SSAO appears to be the only enzyme present in these blood vessels able to catabolize histamine. [ABSTRACT FROM AUTHOR]

Determination of diamine oxidase (DAO) activity in rat liver preparations by measuring the formation of radioactive δ-pyrroline fromC-putrescine is complicated by the complexity of competing metabolic pathways. This can lead to complete masking of the DAO activity present when rat liver homogenates are used as the enzyme source. However, subcellular fractionation of rat liver homogenates makes it possible to detect some putrescine oxidizing activity in the microsomal fraction when assayed at pH 8.5. When 1 m M putrescine was used as the substrate, over 90% of this activity was inhibited by 6×10 M selegiline (deprenyl), indicating that monoamine oxidase (MAO) rather than DAO activity was being measured. The observed activity was also interfered with by agents that reduced acetylation processes and polyamine synthesis. A different picture appears when μ M concentrations of putrescine are used: in these conditions all interference is strongly reduced and DAO activity can be measured in rat liver microsomes. Furthermore, kinetic studies on deaminative oxidation ofC-putrescine at concentrations from 1 μ M to 5 m M confirm the existence of two enzymes: one with a high affinity for the substrate and similar to intestinal mucosa DAO in its sensitivity to α-aminoguanidine, and the other one with a low affinity and selegiline-sensitive. [ABSTRACT FROM AUTHOR]

In rat lung microsomes, an enzyme showing high histaminase activity is present. The oxidation of histamine is dependent on the presence of two enzymic activities, both inhibited by alpha-aminoguanidine and by B24, an inhibitor of semicarbazide-sensitive amine oxidases (SSAO) which have benzylamine as preferential substrate. These enzymic activities differ in substrate specificity: one appears to be a classical tissue bound SSAO enzyme with high affinity for benzylamine, the other a diamine oxidase (DAO) with properties that are very different from the classical DAO. This latter enzyme is not inhibition by high histamine concentrations and is more active at pH 8.5 than at pH 7.4. [ABSTRACT FROM AUTHOR]

Treatment with Aroclor 1254 produces a decrease of diamine oxidase (DAO) activity in quail liver microsomes evaluated, on deamination ofC-putrescine and of histamine. The inhibition observed with theC-putrescine assay has peculiar behavior; it increase with the increase ofC-putrescine concentrations until it produces values of extracted radioactivity which are less than the blanks which do not contain proteins. This effect is reserved by dicyclohexylammonium, an inhibitor of spermidine synthase (SPDS). This paper shows that SPDS rapidly decreases the putrescine concentration during the assay of DAO in tissues, particularly when SPDS is increased by induction with Arocolor. [ABSTRACT FROM AUTHOR]

In quail liver microsomes the metabolism of histamine is prevalently sustained by diaminoxidase (DAO). Treatment with phenobarbital (PB) and clofibrate (CF) does not modify DAO activity, while that with Aroclor 1254 (PCB) and β-naphtoflavone (BNF) significantly decreases it. The decrease of DAO activity produced by these substances is not dependent on their direct inhibition of the enzyme. DAO decrease might represent a further possibility to discriminate among different inducers; moreover, it implies that histamine metabolism might be decreased, in quail liver, by some classes of inducers. [ABSTRACT FROM AUTHOR]

Beta-aminopropionitrile (BAPN) is an inhibitor of pig plasma benzylamine oxidase. BAPN is oxidized by benzylamine oxidase. Inhibition develops in a time-dependent fashion upon incubation of BAPN with the enzyme in the absence of substrate. The product of oxidation of BAPN by benzylamine oxidase, cyanacetaldehyde, was identified and prepared by synthesis. It is an irreversible inhibitor of the enzyme. [ABSTRACT FROM AUTHOR]

Male adult quails were treated with a single intraperitoneal dose of Aroclor 1254 mg/kg. The animals showed increases in hepatic weight and benzopyrene hydroxylase activity which were continuous up to 168 h after the treatment. At 96 h after treatment the activity of diamine oxidase (DAO) in the microsomal fraction was significantly decreased whereas that of spermidine synthase seemed to increase. [ABSTRACT FROM AUTHOR]