Histamine Metabolism in Healthy Subjects before and during Treatment with Aminoguanidine

Abstract

Three healthy subjects were given intravenous infusions of ¹⁴C-histamine, one infusion before and another during aminoguanidine treatment. Urine was analyzed for ¹⁴C-histamine and its radioactive metabolites, and also for total histamine, methylhistamine, and methyl-imidazoleacetic acid. The general metabolic patterns of exogenous (radioactive) and endogenous (non-radioactive) histamine were found to be qualitatively similar. Aminoguanidine treatment a) abolished the excretion of radioactive imidazoleacetic acid, b) increased the excretion of both radioactive methylhistamine and total methylhistamine, c) had little effect on the excretion of histamine and methylimidazoleacetic acid. Some evidence was obtained for impaired oxidation of methylhistamine during aminoguanidine treatment. The informative value of measurements of histamine, methylhistamine and methylimidazoleacetic acid in human urine under different conditions is discussed.