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Phorbol myristate acetate stimulates formation of diphosphoinositide in rat mast cell granules
M Kurosawa1, Y Okayama, S Kobayashi
1First Department of Internal Medicine, Gunma University School of Medicine, Maebashi, Japan.
Abstract:
Rat mast cell granules were obtained by homogenization of highly purified rat mast cells and isolated in a Percoll gradient. Diphosphoinositide (DPI) synthesis in rat mast cell granules was assayed by measuring the incorporation of 32P from [gamma 32P]ATP into DPI in the absence of exogenous phosphatidylinositol (PI). Lipids were isolated with methanol/chloroform/HCl and were separated by thin-layer chromatography on oxalic acid impregnated silica gel plates. DPI areas were identified by staining with iodine, scraped and measured for 32P radioactivity. The addition of phorbol myristate acetate (PMA) to the granules caused an increase of 32P incorporation from [gamma 32P]ATP in the DPI fraction, which can be catalyzed by PI kinase. This effect of PMA in the DPI synthesis was dose dependent and maximal effects were observed at 10 ng/ml.
Insights
Phorbol myristate acetate (PMA) stimulates diphosphoinositide (DPI) synthesis in rat mast cell granules. This indicates that PMA activates phosphatidylinositol (PI) kinase, crucial for DPI production in these cells.
Area of Science:
- Biochemistry
- Cell Biology
- Immunology
Background:
- Rat mast cells are key players in allergic responses.
- Mast cell degranulation involves complex signaling pathways.
- Phosphoinositide metabolism is critical for cellular signaling.
Purpose of the Study:
- To investigate diphosphoinositide (DPI) synthesis in isolated rat mast cell granules.
- To determine the effect of phorbol myristate acetate (PMA) on DPI synthesis.
- To explore the role of phosphatidylinositol (PI) kinase in this process.
Main Methods:
- Rat mast cells were purified and homogenized to obtain granules.
- DPI synthesis was measured by 32P incorporation from [gamma 32P]ATP.
- Lipids were extracted and separated using thin-layer chromatography.
- Radioactivity in the DPI fraction was quantified.
Main Results:
- Rat mast cell granules synthesized DPI in vitro.
- PMA significantly increased 32P incorporation into DPI.
- This effect was dose-dependent, with maximal stimulation at 10 ng/ml PMA.
- The observed DPI synthesis is likely catalyzed by PI kinase.
Conclusions:
- PMA activates PI kinase in rat mast cell granules.
- This activation leads to enhanced DPI synthesis.
- These findings contribute to understanding mast cell signaling pathways.