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From the Laboratory of Clinical Investigation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20014
Abstract
Rat peritoneal mast cells contain peroxidase as demonstrated both histochemically and enzymatically. This enzyme is localized to the mast cell granule where it is concentrated along with histamine and superoxide dismutase (SOD). Rat mast cell degranulation initiated by 48/80 produced a significantly larger percentage of net histamine release than of either peroxidase or SOD. Examination of isolated mast cell granule preparations revealed that histamine was readily displaced from the granule upon exposure to physiologic NaCl solutions and that NaCl solutions of sufficient molarity to dissolve the granular matrix were required to solubilize the bulk of peroxidase and SOD. Therefore, we washed 48/80 treated mast cells with hypertonic NaCl solutions in order to partly dissolve the extracellular granules. A 3.9-fold increase in supernatant peroxidase was produced by this washing without an accompanying commensurate increase in histamine or loss of the capacity of the cells to exclude trypan blue. Based upon these observations, there appeared to be three distinct sources of biologically active mediators generated as a consequence of mast cell degranulation: preformed, readily displaced molecules such as histamine and serotonin; newly generated molecules such as slow-reacting substance of anaphylaxis (SRS-A), and the prostaglandins; and granule matrix associated activities such as peroxidase, SOD, heparin, chymotrypsin, and others. Assessment of the molecules released into the supernatant of degranulated mast cells may therefore indicate only a portion of the mediators actually discharged from the mast cell. The granule matrix-associated activities may be transposed more slowly and cause more subtle and delayed responses. Among the potential activities relevant to immediate hypersensitivity is the capacity of the granule to inactivate SRS-A as well as superoxide
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Footnotes
1 Current address: Dr. William R. Henderson, Division of Allergy and Infectious Diseases, Department of Medicine, University of Washington, Seattle, Washington 98195.
2 Address reprint requests to: Dr. Michael Kaliner, Laboratory of Clinical Investigation, National Institute of Allergy and Infectious Diseases, Bldg. 10, Rm 11N250, National Institutes of Health, Bethesda, Maryland 20014.
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