a-Department of Biological Chemistry, b-Department of Pharmacology and

The effect of altering the abundance of precursors and inhibitors of prostaglandin formation b,y dietary supplements of fish oil was investigated in dogs with experimentally induced myocardial infarction. Prior to induction, 10 male monqrel doqs were fed standard dog chow supplemented with 25 % of the total calories as menhaden oil for 36 to 45 days. The fatty acid composition of the lipids in plasma and platelets chanqed to reflect the increased intake of polyunsaturated fatty acids of the n-3 type. Thrombosis and subsequent infarction was induced by electrical stimulation of the left circumflex coronary artery of amhulatory doqs that were monitored b.y telemetry. Upon stimulation of control animals, the frequency of ectopic beats rose from less than 10 % at the beginning to about 80 % after 19 hours. In contrast, the oil-fed dogs maintained a more normal ECG pattern, showing less than 30 % ectopic beats after 19 hours. In these animals, the size of infarction (measured by formazan formation) was 3 % of the left ventricle compared to 25 % in the control animals. The results suggest that dietary supplementation with fish oil may be beneficial in reducing myocardial damage associated with coronary artery thrombosis