Effect of fish oil supplementation on aortic compliance in rats: role of the endothelium

Arterial compliance improves with dietary fish oils in patients with high c ardiovascular risk. Since fish oils alter prostaglandin metabolism and the L-arginine-nitric oxide pathway, and since compliance may be modified by va soactive substances, the effect of the endothelium and some of its derivati ves on aortic complaince were examined. Rats were randomly allocated to four groups, the first of which fed only th e regular chow. The remaining three groups were fed the chow supplemented b y daily gavage with either coconut, fish or safflower oil for 8 weeks. The thoracic aorta was removed and six 2 mm rings obtained. Rings were paired a nd one from each pair treated with either NW-nitro-L-arginine, indomethacin or de-endothelialized. A diameter-tension curve was initiated from wire to uch position using incremental increases in wire distance until no further response observed. The data was transformed to a diameter-pressure relation ship and fitted with a linear equation, the slope of which related directly to compliance. De-endothelialization (slopes: control vs de-endothelialized: 9.05+/-0.15 v s 8.31+/-0.24; P < 0.05) and indomethacin (slopes: control vs indomethacin: 9.11+/-0.15 vs 7.76+/-0.37; P< 0.05) significantly decreased arterial comp liance as did dietary fish oils (slopes: control vs n-3: 9.16+/-0.11 vs 7.8 4+/-0.39; P< 0.05). No further effect was seen with indomethacin in the fis h oil treated group. It is concluded that the endothelium and in particular, endothelium derived prostanoids, contribute to vessel compliance. We also conclude that fish o ils have a similar action to indomethacin, leading to the increase in aorti c stiffness observed.