The demonstration of histamine release in clinical conditions: a review of past and present assay procedures.

Topics related to the measurement of histamine in human plasma and other body fluids are reviewed. These include (1) an overview of the data obtained by the biological, fluorometric and radioenzymatic assays over the past 45 years; (2) the various modifications of the radioenzymatic isotopic assay of histamine and the development of a single extraction step assay; (3) a compilation of values obtained in our laboratory by the radioenzymatic assay of histamine levels in various body fluids in disease states associated with abnormal histamine production or release; and (4) factors that affect histamine levels in plasma and some experimental considerations for monitoring changes in free histamine levels. The last topic includes a discussion of the halflife of histamine in the circulation, its clearance across various vascular beds, and the fact that capillary endothelial cells are one site of inactivation of circulating histamine.