THE EFFECT OF ENZYME INHIBITORS ON HISTAMINE CATABOLISM IN MAN

Abstract The catabolism of histamine was studied in three female psychiatric patients by analysis of the [14C]-labelled metabolic products occurring in the urine after a subcutaneous injection of [14C]histamine. Each patient was studied before and during treatment with aminoguanidine or iproniazid. Without treatment the patients had a normal histamine catabolism. Aminoguanidine and iproniazid inhibited the oxidation of histamine to imidazoleacetic acid; iproniazid produed a 50% inhibition of the oxidation of methylhistamine to methylimidazoleacetic acid. After iproniazid a large proportion of the injected [C14]histamine was excreted as methyl [14C]histamine.