Abstract
We studied changes in the fatty acid composition of membrane phospholipids in sarcoplasmic reticulum (SR) and mitochondria (Mt) in the acute ischemic myocardium in the dog with the occurrence of severe ventricular arrhythmia such as ventricular tachycardia. The arrhythmia group (A group) was defined grade 3 or higher in Lown's classification and the others regarded non-arrhythmia group (NA group) . Total phospholipid contents of SR and Mt decreased significantly in the ischemic myocardium for 1 and 3 hrs in both of A and NA groups, and a significant decrease in arachidonic acid was noted in SR of A group. By treating SR from the normal heart muscle with exogenous phospholipases (PLase) A2and C, marked reduction in total phospholipid contents were observed in treatment with PLase C. Treatment with PLase A2brought similar reduction in arachidonic acid in A group. These results suggest that membrane degradation occurs with the activation of PLase C in the acute ischemic myocardium and further advances with the activation of PLase A2, mainly the release of arachidonic acid, resulting in the occurrence of severe ventricular arrhythmias in the acute ischemic myocardium.
