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Dietary Canola Oil Modifies Myocardial Fatty Acids and Inhibits Cardiac Arrhythmias in Rats^1,2,3,

Cardiac Research Unit, CSIRO Division of Human Nutrition, Adelaide, SA5000, Australia

Previous research showed that dietary fish oil was potently antiarrhythmic in rats but olive oil was not. This study was designed to test the hypothesis that canola oil, another major dietary source of oleic acid additionally containing the (n-3) polyunsaturated fatty acid -linolenic acid [18:3(n-3)], can reduce vulnerability to cardiac arrhythmia in rats. Rats were randomly assigned to one of four experimental diet groups for 12 wk. The fat source in the diets was 12% olive (63% oleic acid), canola (55% oleic, 8% -linolenic acid), soybean [50% linoleic 18:2(n-6), 7% -linolenic acid] or sunflower seed oil (64% linoleic acid). Arrhythmias were induced by coronary artery occlusion and reperfusion. Incidence of ventricular fibrillation, mortality and arrhythmia score during reperfusion were significantly lower in rats fed the diet containing canola oil than in those fed the olive oil diet. No difference in the severity of arrhythmias was seen in groups fed diets containing soybean or sunflower seed oils. Analysis of myocardial phospholipid fatty acids showed that consumption of canola oil decreased the ratio of (n-6)/(n-3) polyunsaturated fatty acids relative to the other diets, as does dietary fish oil. These results suggest that regular substitution of canola oil for other dietary lipid sources may assist in reducing the likelihood of a transient ischemic event leading to life-threatening cardiac arrhythmias, but the effectiveness of -linolenic acid is reduced by high levels of linoleic acid.

KEY WORDS: • reperfusion • (n-3) fatty acids • canola • arrhythmia • -linolenic acid • rats

¹ Presented in part at a meeting of the Atherosclerosis Discussion Group, "Fatty acids, atherosclerosis and coronary heart disease," September 1993, Cambridge, U.K. [McLennan, P. L. (1993) Fatty acids and arrhythmia] and presented in full at the 1994 Annual Meeting of the International Society for Heart Research, Australasian Section, August 1994, Adelaide, Australia [McLennan, P. L. & Dallimore, J. A. (1994) Alpha-linolenic acid (18:3, n-3) in canola oil but not soybean oil, inhibits reperfusion-induced arrhythmias. J. Mol. Cell. Cardiol. (in press)].

² Supported by Meadow Lea Foods, Sydney, Australia.

³ The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.

⁴ To whom correspondence and reprint requests should be addressed.

Manuscript received 5 July 1994. Revision accepted 4 October 1994.