Mast Cells and Tissue

The observation that the basophilic granulocytes of blood are much richer in histamine than any other blood constituent (2) suggested that the histamine of tissues might be similarly located in association with basophilic material; i.e., in the mast ceils. Riley and West (3, 4), following observation of fluorescent histamine liberators in mast cells (5), reported a positive correlation between the qualitatively estimated frequency of mast cells and the histamine content of the same tissues. Their work was later extended to include histamine and heparin assays in mast cell tumors from dogs (6). Mas t cells have a very irregular distribution not only over the body as a whole but within individual tissues as well. Measurements of the distribution of histamine and mast cells within different regions of the same tissue therefore seemed likely to provide information useful in determining whether the mast cells in fact contain the tissue histamine. Such measurements have been made with adjacent frozen-dried sections of dog skin and lung in which the mast cell distribution is particularly irregular. In one series identical sections were used for both histamine measurements and mast cell counts. Measurements of histamine and mast cells were also made in sections from dog fiver, heart, skeletal muscle, and kidney as well as beef liver capsule and parenchyma. The values obtained leave no reasonable doubt that mos t of the tissue histamine is located in mast cells.