Effects of dietary oleic-rich oils (virgin olive and high-oleic-acid sunflower) on vascular reactivity in Wistar-Kyoto and spontaneously hypertensiverats

The effects of two monounsaturated fatty acid (MUFA)-rich diets, containing virgin olive oil (OO) and high-oleic-acid sunflower oil (HOSO), on develop ment of vascular response from isolated thoracic rat aorta and lipid compos ition and fatty acid composition were studied and compared with samples fro m rats fed on a control diet. Dietary MUFA oils were fed for 6 weeks to spo ntaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats from 4 weeks of a ge. The maximum contraction of aortic ring preparations in response to phen ylephrine (10(-6) m) was significantly decreased in SHR rats fed with OO (0 .81 (SEM 0.05) v. 1.18 (SEM 0.09) g, P<0.01) and treatment with HOSO did no t alter the phenylephrine-induced contractions. The relaxant responses to a cetylcholine (10(-5) m) were significantly enhanced (30.03 (SEM 0.70) v. 18 .47 (SEM 0.28) %, P<0.001) in the rings from SHR rats treated with OO, and were more pronounced than in WKY rats (P<0.05). In the same way, OO attenua ted the dose-response curves induced by phenylephrine (10(-8)-10(-5) m) fro m SHR rats, accompained with a slower contraction. These results suggest th at only the chronic feeding of OO diet was able to attenuate the vascular r esponse of rat aorta. In addition, an increase in phospholipid content (186 .7 (SD 3.2) v. 159.1 (SD 11.3) g/kg, P<0.01) and changes in the fatty acid composition of aorta (mainly a decrease in arachidonic acid) could contribu te to improving endothelial function. Therefore, the effects can not be att ributed exclusively to the content of MUFA (mainly oleic acid). Other compo nents of OO, such as polyphenols, not present in HOSO, may help to explain the vascular protective effect of OO consumption.