Measurement of urinary histamine: Development of methodology and normal values

A small portion of the histamine that circulates through the kidney is excreted intact. Thus, the measurement of histamine in urine may be employed to monitor fluctuations in plasma histamine and has several advantages: stability, accessibility, and the opportunity for retrospective analysis. A method for measuring urine histamine was developed based on cation-exchange chromatography, organic solvent extraction, o-phthalaldehyde condensation, and measurement of fluorescence. However, because the histamine measured by this procedure was higher than that measured by other techniques, a portion of each sample was digested with diamine oxidase and the difference between the two portions of each sample, after isolation and fluorescent assay, was taken to reflect histamine. Normal urinary histamine levels of 13 ± 8 ng/ml, 14 ± 9 μg/24 hr, or 14 ± 72 ng/mg creatinine/ml were found. Male and female subjects excreted equivalent concentrations; spot, short-timed, or 24-hr collections provided equivalent results; and histamine in frozen urine was stable ⩾6 mo. Two patients with systemic mastocytosis and two with idiopathic anaphylaxis had elevated urine histamine levels. Monitoring urine histamine may be useful in assessment of conditions in which histamine plays a role.