Metabolism of¹⁴C‐Histamine in Domestic Animals

Abstract

Abstract The metabolism of 14 C‐histamine injected i.v. in goats has been studied previously. The present study was undertaken to examine whether the metabolic pattern of 14 C‐histamine found in goats is characteristic for ruminating species. The urinary 14 C‐metabolites of i.v. injected 14 C‐his‐tamine to cows and sheep were quantitated by means of isotope dilution technique and paper chromatography. During the first week after injection 74–84 % and 93–99 % of the injected radioactivity was found in sheep and cow urine, respectively. Only 1 % of the radioactivity could be accounted for in the feces and less than 0.03 % in the cow milk. Known metabolites accounted for 84–91 % and 97 % of the urinary radioactivity for sheep and cow, respectively. The metabolic pattern for 14 C‐histamine degradation in sheep and cow did not differ much. As in goats, the oxidative deamination of histamine to imidazoleacetic acid and imidazoleacetic acid riboside seemed to be the only pathway of quantitative importance. Both in sheep and cows histaminol was found to be a metabolite of i.v. injected 14 C‐histamine accounting for about 2 % of the urinary radioactivity. In cows the specific radioactivity of histamine was found to be up to 24 times larger than that for 1.4 methylimidazoleacetic acid.