Degradation of phospholipids and triacylglycerol,and accumulation of fatty acids in anoxic myocardial tissue,disrupted by freeze-thawing

Summary The degradation of lipids by endogenous hydrolytic activity has been studied in rat cardiac tissue deliberately damaged by freezing and thawing prior to storage under anoxic conditions.Aliquots of the freeze-thawed material were kept at 37°C under an atmosphere of N₂ up to 120 minutes. Triacylglycerol was hydrolyzed at a rate of 0.14 mol fatty acids per minute per gram dry weight of tissue. Hydrolysis of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) was associated with proportional production of lyso PC and lyso PE, respectively. This finding indicates that the activity of lysophospholipase is negligible in autolyzing cardiac tissue. The rate of hydrolysis of PC and PE was found to be 0.10 and 0.06 mol per minute per gram dry weight of tissue. The observation that lyso PC and lyso PE mainly contained saturated and mono-unsaturated fatty acids indicates that phospholipase A₂ rather than A₁ is active in autolyzing cardiac tissue. The accumulation of fatty acids corresponded with the loss of triacylglycerol and phospholipids from the tissue during 120 minutes of autolysis.