Diamine oxidase and cadaverine metabolism.

We have recently presented evidence that diamine oxidase is rcsponsiblc for a portion of the metabolism of histamine in several species (1, 2). This evidence is largely based on the alteration of histamine metabolism produced by compounds which are known to inhibit diamine oxidase in vitro. The inhibitors used were isonicotinylhydrazine (3) and aminoguanidine. The latter is reported to be the most powerful inhibitor in vitro known (4). In order to investigate further this apparent inhibition of diamine oxidase in viva, it seemed desirable to use as a substrate some compound with a structure suggesting metabolism by diamine oxidase only. The compound selected was cadaverine (1,5-diamino-n-pentane). Cadaverine is the most frequently used substrate for diamine oxidase in vitro and is reported to be the compound most readily attacked by diamine oxidase (5). We have prepared cadaverine labeled with radioactive carbon and have shown that it is largely metabolized by diamine oxidase in mice and rats. The action of aminoguanidine and isonicotinylhydrazine in preventing the destruction of cadaverine parallels their effect on histamine metabolism. This provides further evidence that diamine oxidase is one of the enzymes involved in histamine metabolism in rats and mice.