Myocardial lesions in rats fed rapeseed oil. I. Influence of strain of rats.

The influence of strain of rat on the development of myocardial lesions was investigated in an experiment which included two factors: strain (Wistar, Sherman, Chester Beatty (Hooded), and Sprague-Dawley from two sources designated Sprague-Dawley A, Sprague-Dawley C) and diet (5% corn oil, 20% corn oil, and 20% Brassica napus var. Zephyr rapeseed oil). Groups of 30 rats, housed 2 per cage, from each of three different strains of rats and groups of 10 rats, housed 2 per cage, from one strain of rats (Hooded) were fed semisynthetic diets containing the test oils for 16 weeks on an ad libitum basis. Rats of the Hooded strain consumed considerably less feed and grew at a significantly (P less than 0.01) slower rate than did rats of the Sprague-Dawley C strain, which in turn ate less and grew significantly (P less than 0.01) slower than rats of the other three strains. No marked differences were observed in the fatty acid composition of total cardiac lipids among strains. Rats from all strains except Hooded fed the diet containing 20% Zephyr RSO had a significantly (P less than 0.001) higher incidence of myocardial lesions than rats fed the 20% corn oil diet which in turn had a significantly (P less than 0.001) higher incidence than rats fed 5% corn oil. Similarly, significantly (P less than 0.05) more Sprague-Dawley C rats had myocardial lesions than Sprague-Dawley A rats regardless of diet. None of the Hooded rats fed the diet containing 20% Zephyr RSO developed myocardial lesions whereas all other strains fed this diet developed a high incidence of myocardial lesions.