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Updated: Aug 10, 2026
Investigating Mast Cell Secretory Granules; from Biosynthesis to Exocytosis
Published on: January 26, 2015
Rat mast cells permeabilized with Sendai virus secrete histamine in response to Ca2+ buffered in the micromolar range
Abstract:
In the presence of low extracellular Ca2+, Sendai virus generates permeability lesions in the membrane of rat mast cells. This causes leakage of intracellular phosphorylated metabolites and lactate dehydrogenase; it also permits uptake of normally impermeant aqueous solutes such as the complex of Ca2+ with N-hydroxyethylethylenediaminetriacetic acid. We have used this system to buffer the concentration of cytosol Ca2+ in the micromolar range and thus to cause release of the contents of the secretory granules such as histamine and beta-N-acetylglucosaminidase. We argue that such release occurs by a normal exocytotic secretory mechanism for the following reasons. (1) While leakage of cytosol components is progressively inhibited by Ca2+ in the range 1-10 microM, release of histamine is dependent on Ca2+ in this range. Higher concentrations of Ca2+ are inhibitory to both permeabilization and histamine release. (2) While leakage of phosphorylated metabolites is enhanced in metabolically inhibited cells and the leakage of lactate dehydrogenase is insensitive to metabolic inhibition, the release of histamine and beta-N-acetylglucosaminidase is strictly dependent on an intact metabolic process.
Insights
Sendai virus creates membrane pores in rat mast cells, allowing calcium buffering. This triggers exocytosis, releasing histamine and other granule contents via a metabolically dependent process.
Area of Science:
- Cell Biology
- Virology
- Immunology
Background:
- Sendai virus induces membrane permeability in rat mast cells under low extracellular calcium conditions.
- This viral-induced permeability allows for the leakage of intracellular components and uptake of specific solutes.
Purpose of the Study:
- To investigate the mechanism of secretory granule release from mast cells using Sendai virus-induced permeability.
- To determine if the release of granule contents occurs via a standard exocytotic pathway.
Main Methods:
- Utilizing Sendai virus to create controlled membrane lesions in rat mast cells.
- Buffering intracellular calcium (Ca2+) concentrations in the micromolar range.
- Measuring the release of specific intracellular components (phosphorylated metabolites, lactate dehydrogenase) and granule contents (histamine, beta-N-acetylglucosaminidase).
Main Results:
- Calcium (Ca2+) concentration in the 1-10 microM range was critical for histamine release, while higher concentrations inhibited both permeabilization and release.
- Leakage of cytosol components was differentially affected by Ca2+ and metabolic state, unlike granule content release.
- Release of histamine and beta-N-acetylglucosaminidase was dependent on an intact cellular metabolic process.
Conclusions:
- Sendai virus-induced mast cell permeabilization provides a model for studying exocytosis.
- The release of histamine and beta-N-acetylglucosaminidase from mast cells occurs through a calcium-dependent, metabolically active exocytotic mechanism.
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