The Presence and Measurement of Methylhistamine in Urine

Abstract

Methylhistamine (I-methyl-4-(@aminoethyl)imidazole) is a major metabolite of administered histamine in most species, including man (2), and methylhistamine has also been found in urine of rats after the administration of histidine (3).Methylhistamine was determined in these experiments by an isotope dilution technique after the administration of radioactive material.No method is available to measure the normal excretion of methylhistamine; in fact, the only evidence of methylhistamine in the urine of untreated animals rests on the presence of ninhydrin-reacting material on paper chromatography of a fraction of urine (4).In the present paper, evidence is presented that methylhistamine is found in human urine and a method for measuring methylhistamine, as dinitrophenylmethylhistamine, is described. EXPERIMENTAL PROCEDUREMaterials-Urine was collected from laboratory personnel for 24 hours in jugs containing 15 ml of 6 N HCl and 15 ml of toluene.The diet of people contributing serial samples was kept as constant as feasible.Urine kept at 4" for over 4 months showed no change in content of either methylhistamine or histamine.Most chemicals were obtained from commercial sources.FTNI was synthesized from 2-fluoronaphthalene (5).The authors are most grateful for methylhistamine, a gift of R. W. Schayer and Y. Kobayashi, and for radioactive methylhistamine, prepared (6) from 14C-adenosylmethionine, a gift of S. H. Snyder and J. Axelrod.A solution of FTN was made by dissolving 0.05 g of the crystalline material in 1 ml of dioxane; 0.05 g of FBD or CTB was dissolved in 1 ml of absolute ethanol; 0.24 ml of FDB was dissolved in 5 ml of absolute ethanol; 10 mg of DNP were dissolved in 1 ml of water.Chromatography-Thin layers of silica gel (0.25 mm thick), were prepared by spreading on glass a suspension of 30 g of Adsorbosil-I (Applied Science Laboratories) in 55 ml of water.The plates were dried in air and heated at 105" for from 3 to 48 hours before use; within this range, the time of activation was