title: Inhibition of enzymic and non-enzymic lipid peroxidation of flounder muscle sarcoplasmic reticulum by pretreatment with phospholipase A2.
abstract: Sarcoplasmic reticulum, isolated from the muscle of winter flounder (Pseudopleuronectes americanus), was preincubated with phospholipase A2 to determine the effects of enzymic and non-enzymic lipid-peroxidation systems. Eicosapentaenoic acid (20:5) was preferentially released by phospholipase A2, but the percentage of docosahexaenoic acid (22:6) in the free fatty acids was similar to the percentage in membrane total fatty acids. A decrease in the production of both thiobarbituric acid-reactive substances and lipid hydroperoxides was observed in both the enzymic and non-enzymic peroxidation systems upon preincubation with phospholipase A2. Addition of palmitic acid or lysophosphatidylcholine did not inhibit either peroxidation system. Non-enzymic peroxidation was inhibited by the addition of beta-glycerophosphate, but enzymic peroxidation was apparently unaffected. A model is proposed to explain the inhibitory effect of phospholipid hydrolysis on lipid peroxidation in both systems, suggesting that fatty acids are structurally realigned upon hydrolysis, leading to decreased free-radical chain propagation. Additional factors appear to contribute to inhibition of enzymic peroxidation.
mesh_terms: D000818:Animals; D005399:Fishes; D066298:In Vitro Techniques; D008054:Lipid Peroxides / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects; D010740:Phospholipases / Q000494:pharmacology*; D010741:Phospholipases A / Q000494:pharmacology*; D054467:Phospholipases A2; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*
chemical_list: D008054:Lipid Peroxides; D010740:Phospholipases; D010741:Phospholipases A; D054467:Phospholipases A2