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Ca2+ release in the endoplasmic reticulum of guinea pig peritoneal macrophages
Abstract:
Passive permeability of the endoplasmic reticulum of saponin-treated macrophages to Ca2+ was studied by the filtration method using 45Ca. The Ca2+ release from the endoplasmic reticulum of macrophages was enhanced by the presence of submicromolar concentrations of Ca2+ in the medium. The Ca2+ release was enhanced by caffeine, and suppressed by MgCl2. These phenomena are similar to the Ca2+-induced Ca2+ release reported for the sarcoplasmic reticulum of skeletal muscle. On the other hand, adenine suppressed the Ca2+ release from the endoplasmic reticulum, while it reportedly enhanced the Ca2+-induced Ca2+ release of the skeletal muscle. The threshold concentration of Ca2+ for the Ca2+-induced Ca2+ release was approximately 10(-8) M in the presence of 0.95 mM MgCl2 in macrophages. The spontaneous spreading of macrophages and spontaneous migration of macrophages were inhibited by adenine, and also by caffeine in spite of the enhancement of the Ca2+-induced Ca2+ release.
Insights
Calcium (Ca2+) release from macrophage endoplasmic reticulum is enhanced by low Ca2+ levels and caffeine, but inhibited by magnesium. This Ca2+ signaling differs from skeletal muscle, impacting macrophage functions.
Area of Science:
- Cell Biology
- Immunology
- Biochemistry
Background:
- Macrophages play crucial roles in immune responses.
- Calcium signaling is vital for cellular functions, including immune cell activity.
- The endoplasmic reticulum is a key organelle for calcium storage and release.
Purpose of the Study:
- To investigate the passive permeability of macrophage endoplasmic reticulum to calcium (Ca2+).
- To characterize the mechanisms of Ca2+ release from macrophage endoplasmic reticulum.
- To compare Ca2+ handling in macrophages with that in skeletal muscle sarcoplasmic reticulum.
Main Methods:
- Utilized saponin-treated macrophages.
- Employed the 45Ca filtration method to study Ca2+ permeability.
- Investigated the effects of various substances (Ca2+, caffeine, MgCl2, adenine) on Ca2+ release.
Main Results:
- Submicromolar Ca2+ concentrations enhanced Ca2+ release from macrophage endoplasmic reticulum.
- Caffeine enhanced Ca2+ release, while MgCl2 suppressed it.
- Adenine suppressed Ca2+ release, contrasting with its effect on skeletal muscle.
- Ca2+-induced Ca2+ release threshold was approximately 10(-8) M with 0.95 mM MgCl2.
- Adenine and caffeine inhibited spontaneous macrophage spreading and migration.
Conclusions:
- Macrophage endoplasmic reticulum exhibits unique Ca2+ release properties distinct from skeletal muscle.
- Ca2+ signaling pathways in macrophages are modulated by caffeine and adenine.
- These findings suggest a role for endoplasmic reticulum Ca2+ dynamics in regulating macrophage behavior and immune function.