Action of inhibitors on monoamine and diamine metabolism in the rat

Abstract

The effects of a series of inhibitors of monoamine oxidase (EC 1.4.3.4) and diamine oxidase (EC 1.4.3.6) and of two chelating agents were studied in rats, with respect to the catabolism of labeled pentylamine and putrescine to radioactive carbon dioxide. D-Tranylcypromine, clorgyline, and deprenyl inhibited oxidation of the monoamine, with essentially no effect on putrescine, under our test conditions. Aminoguanidine inhibited putrescine but not pentylamine oxidation. Iproniazid, isoniazid, and Lilly 51641 affected the catabolism of both amines. Pargyline inhibited putrescine oxidation, apparently in a reversible manner.

Inhibition of diamine oxidase by antimalarial drugs

“…Secondly, BEAVEN and SrIAFF [20] have shown that the assay of histaminase activity with fl-[3H]histamine as substrate provides results equivalent to the assay of DAO activity with [14C]putrescine. Thirdly, there is much evidence that the rate of metabolism of putrescine as we measure it in the rat reflects the activity of DAO [21][22][23]. In this regard one must also consider the possibility that the inhibition of putrescine metabolism could result from inhibition of one or more of the enzymes involved in this pathway, other than DAO.…”