Effect of platelet-activating factor on arachidonic acid metabolism in renal epithelial cells.
We studied the effects of platelet-activating factor (PAF-acether) on phospholipase activity in renal epithelial cells. When platelet-activating factor was added to renal cells prelabeled with [3H]arachidonic acid, it induced the rapid hydrolysis of phospholipids. Up to 26% of incorporated [3H]arachidonic acid was released into the medium from renal cells. After the addition of PAF-acether, the degradation of phosphatidylcholine, phosphatidylinositol and phosphatidylethanolamine were observed. The amount of [3H]arachidonic acid released were comparable to the losses of phosphatidylcholine, phosphatidylinositol and phosphatidylethanolamine. In renal cells biosynthetically labeled by incorporation of [3H]choline into cellular phosphatidylcholine, lysophosphatidylcholine and sphingomyelin, the range of concentrations of PAF-acether-induced hydrolysis of labeled phosphatidylcholine were approximately equal to the amounts of lysophosphatidylcholine produced. We also observed a transient rise of diacylglycerol after the addition of platelet-activating factor to these cells. To test for action of phospholipase C, the accumulations of [3H]choline, [3H]inositol and [3H]ethanolamine were determined. The radioactivities in choline and ethanolamine showed little or no change. An increase in inositol was detectable within 1 min and it peaked at 3 min. These results indicate that platelet-activating factor stimulates phospholipase A2 and phosphatidylinositol-specific phospholipase C activity in renal epithelial cells. These phospholipase activities were Ca2+ dependent. Moreover, PAF-acether enhanced changes in cell-associated Ca2+. These results suggest that the increased Ca2+ permeability of cell membrane stimulates phospholipases A2 and C in renal epithelial cells. Prostaglandin biosynthesis was also enhanced in these cells by platelet-activating factor.
Kawaguchi
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H
Yasuda
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H
D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism*; D002118:Calcium / Q000502:physiology; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D004847:Epithelial Cells; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D050356:Lipid Metabolism; D051379:Mice; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D010972:Platelet Activating Factor / Q000494:pharmacology*; D011453:Prostaglandins / Q000096:biosynthesis; D010738:Type C Phospholipases / Q000378:metabolism
D001095:Arachidonic Acids; D010972:Platelet Activating Factor; D011453:Prostaglandins; D016718:Arachidonic Acid; D010741:Phospholipases A; D054467:Phospholipases A2; D010738:Type C Phospholipases; D002118:Calcium