Does platelet aggregation play a role in the reduction in localized intimal proliferation in normolipidemic pigs with fixed coronary artery stenosis fed dietary fish oil?

In order to investigate the effect of fish oil on intimal proliferation of coronary arteries with a fixed stenosis normolipidemic piglets received a basic diet to which either 9% (w/w) lard (L, n = 8) or 4.5% (w/w) lard and 4.5% (w/w) mackerel oil (ML, n = 8) was added for 4 months. Stenosis was applied by implanting a 4.0 X 2.0 mm (i.d.) Teflon constrictor around the left anterior descending coronary artery (LADCA) (o.d. 2.7 +/- 0.1 mm). During the dietary period ADP-induced platelet aggregation in whole blood was higher in L than in ML. Partial replacement of 20:4 n - 6 by 20:5 n - 3 fatty acids in the platelet membranes of ML may have altered platelet aggregation by changes in eicosanoid synthesis. The plasma cholesterol and triglyceride levels did not change in L, but decreased in ML. At the end of the 4-month dietary period the animals were again anesthetized and regional myocardial perfusion (radioactive labelled microspheres) and systolic segment length shortening (SLS) were measured while the hearts were paced at 160 pulses/min. Perfusion and SLS of non-LADCA nourished segment were similar for L and ML. However, transmural flow to the LADCA perfused myocardium was impaired in both groups, but the deficiency in endocardial perfusion was considerably larger in L than in ML, resulting in a larger loss of SLS in the former. Remote (2-3 cm from the site of the constrictor) luminal encroachment was minimal (less than 2%) in both groups, but at the site of the constrictor there was significant encroachment in both groups which was higher in L (62 +/- 7%) than in ML (11 +/- 4%). It is thought that in these normolipidemic pigs the reduction in platelet aggregation may play a role in the smaller intimal proliferation of the fish oil-fed animals.