Simultaneous determinations of histamine and N tau-methylhistamine by high-performance liquid chromatography-chemiluminescence coupled with immobilized diamine oxidase.

A method for the simultaneous determinations of histamine and its metabolite N tau-methylhistamine by HPLC-chemiluminescence coupled with immobilized diamine oxidase was developed. The method was based on the determination of chemiluminescence formed by the reaction of a luminol-ferricyanide mixture in alkaline medium with hydrogen peroxide which is one of the metabolic products of histamine and N tau-methylhistamine formed by diamine oxidase. HPLC with postcolumn derivatization resulted in good separation of the two amines and gave linear relationships between the concentrations of both and their chemiluminescence intensities. The lower limits of chemiluminescent detection of histamine and N tau-methylhistamine were 5 and 10 pmol, respectively. The immobilized column showed good operational stability for more than 1 month, during which period 200 samples were analyzed. With this system, the histamine contents of the cerebral cortex, forestomach, glandular stomach, and kidney of Wistar rats were found to be 0.30, 58, 396, and 2.4 nmol/g wet wt, respectively. These values are very similar to those determined by HPLC-fluorometry. The N tau-methylhistamine contents of these tissues were 0.36, 0.40, 0.72, and 3.8 nmol/g wet wt, respectively. This method will be useful for studying the roles of histamine in both brain and peripheral tissues.