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Growth Rate, Lipid Composition, Metabolism and Myocardial Lesions of Rats Fed Rapeseed Oils (Brassica campestris var. Arlo, Echo and Span, and B. napus var. Oro)^1,2,

Animal Research Institute, Agriculture Canada, Ottawa, Canada, K1A OC6 ^* Animal Pathology Division, Health of Animals Branch, Agriculture Canada, Animal Diseases Research Institute, P. O. Box 1400, Hull, Que., Canada

Fully refined rapeseed oils containing different amounts of erucic acid (Brassica napus var. Oro—1.6%, B. campestris var. Span—4.3%, B. campestris var. Echo and Arlo, i.e., regular rapeseed oil—22.3%) were fed to male and female rats at 20% by weight in their diets. Rapeseed oil high in erucic acid depressed growth. The severity of cardiac lipidosis after 1 week on experimental diets, measured gravimetrically and histologically by oil red O staining, correlated to the erucic acid content in the dietary oil. The ratio of saturated to unsaturated fatty acids in cardiac and hepatic lipids was much lower in the rapeseed oil-fed groups than in the control groups fed corn oil, lard and a stock diet. Prolonged feeding of rapeseed oils produced a trend toward "normalization" in the fatty acid composition of female rat heart and liver and in male rat heart, but not in the male rat liver. Palmitate activation to its CoA ester as well as triglyceride lipase (triolein) activity was normal in all of the experimental groups. Intact heart mitochondria isolated from rats on each of the dietary groups at 1 week on diet showed no marked difference in oxygen uptake or energy production. Homogenates from rat hearts of all experimental groups failed to activate erucic acid to its CoA ester (2% as efficient as palmitic acid) and did not hydrolyze trierucin to any appreciable extent, whereas erucyl carnitine, the metabolically active ester, was readily oxidized. Evidence of myocardial necrosis and fibrosis was found in male rats but not in female rats at 16 weeks of age when rapeseed oils were fed. A low incidence of myocardial lesions was also found in male rats fed the corn oil control diet.

KEY WORDS: • rapeseed oil • erucic acid • myocardial lipidosis • necrotic and fibrotic lesions • fat metabolism • sex differences

¹ Contribution no. 496 from Animal Research Institute, Agriculture Canada, Ottawa, Ontario.

² Abbreviations: Oro = Brassica napus, var. Oro containing 1.6% erucic acid; Span = B. campestris var. Span containing 4.3% erucic acid; RSO = mixture of B. campestris var. Echo (85%) and var. Arlo (15%) containing 22.3% erucle acid.

Manuscript received 4 June 1973.