| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1995: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1994: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
Arachidonic acid as a precursor for eicosanoid is known to be liberated by the hydrolytic action of phospholipase A_2 (PLA_2) on membrane phospholipids. The present study has been undertaken to investigate whether or not the arachidonic acid liberation by diacylglycerol (DAG) lipase from DAG which is produced through the sequential actions of phospholipase D (PLD) and phosphatidate phosphohydrolase (PAPase), is the important pathway upon stimulation in rat peritoneal mast cells. The results obtained are as follows.
1. The arachidonic acid liberation upon stimulation with Ca^<2+> ionophore ionomycin was inhibited by about 50 % by addition of ethanol to suppress phosphatidic acid production through PLD activation, or of inhibitors for PAPase or DAG lipase.
2. The arachidonic acid liberation in response to IgE receptor-dependent stimulation was completely inhibited by ethanol or the inhibitors indicated above.
3. The production of prostaglandin D_2 (PGD_2), a major metabolite of arachidonic acid in rat peritoneal mast cell in response to IgE receptor-dependent stimulation and also ionomycin, was completely suppressed by ethanol or the inhibitors indicated above.
4. Stimulation with melittin, that can specifically activate PLA_2, induced arachidonic acid liberation but not PGD_2 production, while stimulation with ADP ribosylation factor (ARF), that does PLD,induced marked PGD_2 production as well as arachidonic acid liberation both of which were completely suppressed in the presence of ethanol.
These results indicate that in rat peritoneal mast cells stimulus-induced arachidonic acid liberation is contributed by the sequential PLD/PAPase/DAG lipase pathway in addition to PLA_2 pathway, whereas PGD_2 production following arachidonic acid liberation is fully dependent on the PLD-linked lipid metabolism.
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