A method for the assay of histidine decarboxylase activity.

The histamine-forming enzyme histidine decarboxylase (HDC) is induced in various tissues of mice in response to various physiological or inflammatory stimuli including stress, physical exercise, proinflammatory cytokines and hematopoietic cytokines. The induction of HDC also occurs in mast cell-deficient mice. The newly formed histamine produced through the induction of HDC diffuses away from its site of formation without being stored. Therefore, in addition to the release of histamine from mast cells or basophils, the induction of HDC is an important alternative mechanism for supplying histamine. Studies on the newly formed histamine may clarify new physiological or pathological roles of histamine. Here, we introduce a method that we devised for the simultaneous assay of HDC activity of many samples taken from mice. This method is based on (i) a simple method for the preparation of histamine-free enzyme solutions and (ii) a simple manual method for the separation of histamine formed in reaction mixtures containing HDC.