1. The effects of fish oil supplementation on atherosclerosis in different regions of the aorta in rabbits with diet-induced hypercholesterolaemia were studied. Control and experimental rabbits were fed a 1% cholesterol-enriched diet with or without 10% fish oil supplementation (seven in each group), and were killed after 2 weeks of feeding. The ascending, descending and abdominal aortas as well as the pulmonary artery were harvested for analyses of prostanoid production, malondialdehyde, superoxide dismutase activity and cholesterol levels. The tissues from the other seven rabbits of each group were obtained after 6 weeks of feeding for the identification of atherosclerotic lesions by a Sudan IV stain.

2. The cholesterol-fed rabbits had a significantly higher thromboxane B2 production, a lower 6-keto-prostaglandin/thromboxane B2 ratio and a higher malondialdehyde level than the other two groups in the ascending and abdominal aortas as well as the pulmonary artery; this finding paralleled the severity of atherosclerotic lesions. These manifestations were most prominent in the ascending aorta. The fish oil-supplemented rabbits had the most beneficial aortic prostanoid production, attenuated lipid peroxidation and significantly suppressed atherosclerosis.

3. These results suggest that a high-cholesterol diet induces more atherosclerotic lesions, especially on the ascending aorta, in rabbits. A fish oil supplement favours prostanoid production and attenuates lipid peroxidation on all four regions of the great arteries, thus suppressing atherosclerosis in diet-induced hypercholesterolaemic rabbits.

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