title: High content of 22:6 (docosahexaenoate) and active [2-3H]glycerol metabolism of phosphatidic acid from photoreceptor membranes.
abstract: This study describes the content, fatty acid composition and [2-3H]glycerol metabolism of phosphatidic acid of rod outer segment membranes from vertebrate retinas. A relatively high content of phosphatidic acid was observed in rod outer segment membranes isolated from rat, toad and bovine retinas. In bovine retinas, about 65% of the acyl groups of phosphatidic acid were composed of docosahexaenoate. Arachidonate and docosapentaenoate represented about 4 and 5%, respectively, of the total, whereas stearate was the most common saturated acyl chain. An active [2-3H]glycerol metabolism in the phosphatidic acid of these membranes was found when whole retinas were incubated with the precursor for short periods prior to subcellular fractionation. Our results suggested that the pool of phosphatidic acid enriched in docosahexaenoate may arise from de novo biosynthesis or from phospholipid degradation by a phospholipase D enzyme, and that it is not metabolically related, in any major fashion, to the diacylglycerols of rod outer segment membranes.
mesh_terms: D000818:Animals; D002022:Bufo arenarum; D002462:Cell Membrane / Q000378:metabolism; D004075:Diglycerides / Q000378:metabolism; D004281:Docosahexaenoic Acids; D005227:Fatty Acids / Q000032:analysis; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D005990:Glycerol / Q000378:metabolism*; D008297:Male; D008861:Microsomes / Q000378:metabolism; D010712:Phosphatidic Acids / Q000378:metabolism*; D010786:Photoreceptor Cells / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012374:Rod Cell Outer Segment / Q000378:metabolism*; D014316:Tritium
chemical_list: D004075:Diglycerides; D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated; D010712:Phosphatidic Acids; D014316:Tritium; D004281:Docosahexaenoic Acids; D005990:Glycerol