Glucose inhibits insulin release when not promoting the entry of calcium into the beta-cells |
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Authors: | P Bergsten B Hellman |
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Affiliation: | Department of Medical Cell Biology, Biomedicum, University of Uppsala, S-751 23 Uppsala, Sweden |
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Abstract: | The effect of antigen on the metabolism of polyphosphoinositides was investigated in sensitized rat peritoneal mast cells. Addition of antigen to rat peritoneal mast cells prelabelled with [3H]arachidonic acid resulted in a very rapid decrease in the level of phosphatidylinositol 4-phosphate (DPI) within 5 sec, which appeared to precede the breakdown of phosphatidylinositol (PI), while there was no significant decline of PI 4,5-bisphosphate (TPI). The reduced levels of these phosphoinositides returned almost to control or even slightly higher values by 300 sec in parallel with the antigen-stimulated [32P]phosphate incorporation into these lipids. This early and transient disappearance in DPI prior to that in PI was also observed in [3H]glycerol-prelabelled cells. These data suggest that DPI degradation upon stimulation by antigen in mast cells may be an initial step in the histamine release process. |
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Keywords: | PI Phosphatidylinositol DPI phosphatidylinositol 4-phosphate TPI phosphatidylinositol 4,5-bisphosphate PA phosphatidic acid PPI polyphosphoinositides PS phosphatidylserine 1, 2-DG 1,2-diacylglycerol DNP-As PBS phosphate-buffered saline HEPES EGTA HPTLC high-performance thin-layer chromatography |
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