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

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 degrees C under an atmosphere of N2 up to 120 minutes. Triacylglycerol was hydrolyzed at a rate of 0.14 mumol 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 mumol 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.