Increased urinary imidazolepropionic acid, n-acetylhistamine and other imidazole compounds in patients with intestinal disorders

Abstract

In 26 out of a large group of patients with gastrointestinal disorders abnormal urinary imidazole excretion patterns were found. Most frequently excessive or increased amounts of imidazolepropionic acid (ImPA) occurred, and as next N-acetylhistamine was excreted in excess. In a number of cases the latter was accompanied by a substance identified as N-propionylhistamine. It is suggested that these excretory products are bacterial metabolites of histidine, if not absorbed in the intestinal lumen. All 26 patients excreted increased amounts of bacterial metabolites of tyrosine and/or phenylalanine as well: p-OH-phenylacetic and/or p-OH-benzoic acids and phenylacetic and/or benzoic acids respectively. Many patients showed increased urinary 4-amino-5-imidazolecarboxamide, its riboside and an unknown related compound X, especially in a later (recovery) phase when imidazolepropionic acid and N-acetylhistamine already decreased. It is thought that these metabolites are not of bacterial origin.