The influence of some drugs on the determination of diamine oxidase activity [proceedings]

Species-dependent differences of the biochemical properties of diamine oxidase

Diamine oxidase (DAO) from tissues of mice, rats and humans showed different properties with respect to stability and kinetic parameters. DAO-activities in homogenates of rat or human tissues, but not of mouse tissues, rapidly decreased upon storage at -20 degrees C. The Km-value for putrescine was 90 microM in mouse kidney or intestine. In rats different Km-values were observed before (272 microM) and after freezing (102 microM). A similar effect was observed with DAO in human kidney (321 and 39 microM, respectively). Treatment of rats with heparin resulted in a depletion of intestinal DAO and the concomitant appearance of DAO in blood. The enzyme remaining in the intestine showed the lower Km-value.

Rapid characterization and partial purification of various animal amine oxidases

The use of chromatofocusing to obtain a rapid characterization of tissue amine oxidases from various mammals is proposed. This technique yields partially purified enzymes well suited for immunological studies. Chromatofocusing can be also used in a three-step purification of pig kidney diamine oxidase.

Diamine oxidase activity in human melanoma cell lines with different tumorigenicity in nude mice

The activity of diamine oxidase (DO, EC 1.4.3.6.) which converts putrescine into gamma-aminobutyraldehyde in the degradative pathway of polyamine, was studied in 4 human melanoma cell lines, 2 of which produce tumours in greater than 80% of nude mice (M3Dau, M4Beu), whereas the other 2 induce tumours in less than 25% (M1Dor, M2GeB). The activity of DO in these cells varies with the growth rate: 24 h after seeding there is an initial increase in DO activity, followed by a steep decline during exponential growth. At 96 h, when cells reach saturation density, the activity of DO is significantly greater in the highly tumorigenic cell lines than in the poorly tumorigenic cell lines. Kinetic studies show that for the highly tumorigenic lines apparent Km values are 10.6 X 10(-6)M +/- 0.2 (M3Dau) and 14.2 X 10(-6) M +/- 0.6 (M4Beu), whereas for the poorly tumorigenic lines the values are 4.5 X 10(-6) M +/- 0.3. After transplantation into nude mice, the M1Dor cell line, which exhibits a low Km (app.) for DO of which had high Km (app.) value. Km (app.) determination of DO could be an approach for characterizing human melanoma cells differing in their tumorigenic potential in nude mice.

Involvement of diamine oxidase in catabolism of 14C-putrescine in mice in vivo with special reference to the formation of gamma-aminobutyric acid

Tissues of mice killed 2.5 or 30 min after injection of 14C-putrescine, contained 14C-gamma-aminobutyric acid, an unidentified 14C-compound, and unchanged 14C-putrescine. In mice pretreated with aminoguanidine, a powerful inhibitor of diamine oxidase, and then with 14C-putrescine, tissue levels of the radioactive catabolites, gamma-aminobutyric acid and the unidentified compound were markedly reduced. The data suggest that diamine oxidase is involved in the first step of putrescine metabolism and that intestine is the main site for this step. This and other aspects of putrescine metabolism are discussed.

Metabolism of putrescine in the pregnant rat

The in vivo metabolism of 14C-putrescine injected to rats before, during and after pregnancy was studied. Within 30 min of the administration of the isotope 9-12% of the injected radioactivity was recorded as 14CO2 in the expired air and after 5 h 60% was expired. The radioactivity excreted in the urine during the first day following the 14C-putrescine administration consisted of unmetabolized putrescine, gamma-aminobutyric acid (GABA) and some unidentified compound(s). No radioactive polyamines were detected in the urine. After treatment of pregnant rats with the diamine oxidase inhibitor aminoguanidine the expiration of 14CO2 was almost completely inhibited. In the urine increased amounts of unmetabolized putrescine were excreted while the excretion of GABA and the unidentified compound(s) were decreased. In addition 14C-spermidine appeared in the urine. The in vitro metabolism of putrescine was determined by the incubation of different tissues of pregnant and non-pregnant rats with 14C-putrescine. The 14C-metabolites derived via the diamine oxidase pathway (delta 1-pyrroline, GABA, some unidentified compound(s) and carbon dioxide) varied in magnitude with the tissue investigated. GABA was found to be a main metabolite of putrescine in several tissues of the pregnant rat. The content of putrescine and spermidine was elevated in several tissues as well as the blood on the 19th day of pregnancy in rats treated with aminoguanidine, while the content of spermine was unchanged.