Radioenzymatic assay for measurement of tissue concentrations of histamine: adaptation to correct for adherence of histamine to mechanical homogenizers.

Because adherence of histamine to glass is well-known, we tested for its adherence to a mechanical homogenizer commonly used in the extraction of histamine from tissue samples. During 60 sec of homogenization, 15% to 17% of the histamine originally present in the samples "disappeared," and the reason for the disappearance was reversible binding of histamine to the homogenizer. Adding trace amounts of [14C]histamine to each sample before homogenization and measuring the disappearance of radioactivity during homogenization permitted correction for binding to the homogenizer. This technique for correction was validated by the measurement of endogenous concentrations of histamine in the tracheal posterior membranes of six dogs (range of mean concentrations: 0.63 to 1.51 ng/mg wet weight) followed by the measurement of known amounts of exogenous histamine added before homogenization to tracheal tissue samples from the same dogs. In the latter samples, 96 +/- 13% (mean +/- SEM) of the histamine added was measured by our technique. We conclude that binding of histamine to mechanical homogenizers may be an important cause of inaccuracy of the enzymatic assay for the measurement of histamine concentrations in tissue but that such binding may but that such binding may be easily corrected for.