We have identified and quantified the major species of arachidonate-containing phospholipids in proximal tubules by high performance liquid chromatographic and gas chromatographic analyses. Arachidonate was found to comprise 53% of the total mass of fatty acids esterified at the sn-2 position of ethanolamine phospholipids, and 51% of that amount resides in three plasmenylethanolamine species containing the vinyl ethers of palmitaldehyde, oleylaldehyde or stearylaldehyde at the sn-1 position. Choline phospholipids contained 21% arachidonylated species and 33% of that amount resides in a single plasmenylcholine species containing the vinyl ether of palmitaldehyde at the sn-1 position. Ten minutes of hypoxia did not cause a significant change in the total phospholipid mass of ethanolamine or choline phospholipids; however, phosphate analysis of the individual phospholipid molecular species containing esterified arachidonic acid in isolated proximal tubules demonstrated a 24% reduction in the mass of the plasmenylethanolamine molecular species with the vinyl ether of oleylaldehyde at the sn-1 position and a 35% reduction in the mass of plasmenylcholine species with palmitaldehyde at the sn-1 position. These studies underscore the pathophysiological importance of plasmalogen phospholipid hydrolysis and suggest that activation of PLA2s, which utilize endogenous proximal tubule plasmalogen substrates, may play an important role in the early generation of arachidonic acid and accompanying phospholipid catabolism during hypoxic cell injury.
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