Sensitivity of the mink (Mustela vison) liver monoamine oxidase to isoquinoline alkaloids

Abstract

MAO. Note that the inhibitory specificity of mink MAO is virtually unstudied. Only one [11] of the available scarce papers on the catalytic properties of this enzyme reports its sensitivity to two acridine derivatives. Analysis of the effects of benzo[c]phenanthridine alkaloids (sanguinarine and chelerythrine), the diisoquinoline alkaloid berberine, and the drugs Ukrain and Sangviritrin on the mink ( Mustela vison ) liver MAO activity, conducted for the first time, is of doubtless interest for expanding the biochemical studies into the properties of enzymes of domesticated fur-bearing animals. Mitochondrial fragments of the American mink ( M. vison Schreb.) liver were the source of MAO. The liver was excised from mature 2-year-old male minks with a weight of 1.5‐1.7 kg kept under standard conditions in the Kondopoga State Fur Plant [12]. The animals were euthanized by decapitation. The mitochondrial membranes were isolated from tissue homogenates partially purified from the ballast protein by extraction in 0.0075 M potassium phosphate buffer pH 7.4 [13]. The mitochondrial fragments were obtained by freezing at ‐20 ° C with subsequent centrifugation and stored frozen until used. The protein content, determined by biuret method, amounted to 17 ± 2 mg/ml. MAO activity was determined spectrophotometrically (at 420 nm) according to the amount of ammonia formed over 30 min in the enzymatic reaction of oxidative deamination of the monoamines— tyramine hydrochloride, benzylamine hydrochloride, and β -phenylethylamine hydrochloride (Sigma, United States)—with serotonin creatinine sulfate (Reanal, Hungary) according to the modified Conway method with subsequent nesslerization [13]. The samples (final volume, 2.5 ml) contained fragments of mitochondrial membranes in an amount corresponding to approximately 1 mg protein, 0.5 ml of inhibitor (tested preparation) at a specified concentration or 0.5 ml of water (in control experiments), 0.5 ml of 0.01 M phosphate buffer pH 7.4, and 0.5 ml of a substrate at a specified concentration (1 mM tyramine, tryptamine, benzy