Effect of lysophospholipids, arachidonic acid and other fatty acids on regulation of Ca2+ transport in permeabilized pancreatic islets.
The immediate reaction products of PLA2-mediated hydrolysis of phospholipids were tested for their ability to induce Ca2+ mobilization from internal stores in permeabilized ob/ob mouse pancreatic islets. Lysophospholipids and unsaturated fatty acids increased the free Ca2+ concentration in the incubation medium of permeabilized ob/ob mouse pancreatic islets. The potency of the lysophospholipids decreased in the following order: lysophosphatidylcholine = lysophosphatidylglycerol much greater than lysophosphatidylinositol greater than lysophosphatidylserine much greater than lysophosphatidylethanolamine. Arachidonic acid and palmitoleic acid had a potency comparable to lysophosphatidylinositol, while palmitic acid was ineffective. The Ca(2+)-mobilizing effect of inositol-1,4,5-trisphosphate (IP3) in permeabilized islet cells was additive to the lysophospholipid effect, indicating different sites of action. Both Ca(2+)-mobilizing effects were counteracted by the polyamine spermine, while the presence of Mg2+ shifted the Ca2+ concentrations to higher levels. Since not only an activation of a phospholipase C but also an activation of a phospholipase A2 with subsequent generation of lysophospholipids and free fatty acids is reported to occur in glucose-induced insulin secretion, the interaction of the phospholipase C reaction product IP3 with a lysophospholipid or an unsaturated fatty acid may affect the extent and duration of the rise in the free cytoplasmic Ca2+ concentration responsible for initiation of insulin secretion.
Rustenbeck
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I
Institute of Pharmacology and Toxicology, University of Göttingen, Germany.
Lenzen
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S
D000818:Animals; D001095:Arachidonic Acids / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000502:physiology; D005227:Fatty Acids / Q000502:physiology*; D007515:Islets of Langerhans / Q000378:metabolism*; D008246:Lysophospholipids / Q000502:physiology*; D008274:Magnesium / Q000502:physiology; D051379:Mice
D001095:Arachidonic Acids; D002352:Carrier Proteins; D005227:Fatty Acids; D008246:Lysophospholipids; D008274:Magnesium; D002118:Calcium