Since lowering effects of essential fatty acids and vegetable oil on the blood chole sterol level were reported by Tuttle (1), Kinsell et al. (2) and Vles et al. (3), the similar studies were further extended to unsaturated fatty acids of longer chains. The lower ing effects of pure linoleate and arachidonate on the elevated blood cholesterol level were presented by Kinsell et al. (2) and Kingsbury (4). However, the recent study by Beveridge and Connell (5) has shown that the large doses of margarine which contained large amounts of unsaturated fatty acids produced a slight elevation of the blood cholesterol level in humans.The histologically atherosclerotic or atheromatous changes of the tissues in rabbits caused by feeding with the diet containing between 1 and 3% of cholesterol for about 60 days were confirmed by many investigators including the present authors (6). In the present experiments attempts were made to observe the effects of mixing of linoleic acid ethylester in the high cholesterol diet on the atheromatous changes and to compare the difference in the effects of the mixings between the saturated and unsaturated fatty acids.
METHODSTwenty-three young male rabbits weighting about 1.8 kg at the start of feeding were used. The control group consisted of 3 rabbits was given 88 g/day/animal of the artificial diet (defatted CR-1 supplied by the Central Laboratory for Experimental Ani mal, Tokyo). The defatted diet contained 1.5% low fat in which the linoleic acid content was 18.2% according to gaschromatographic analysis. Therefore, the control group re ceived the daily dose of 218 mg of linoleic acid. The other 20 rabbits were given the defatted diet mixed with 1 % of cholesterol, and were used as the high cholesterol diet groups. These groups were divided into three groups. The first group consisted of 5 rabbits was given the high cholesterol diet mixed with 10% of ethyl-linoleate (L-group) .The second group consisted of 5 rabbits was given the high cholesterol diet mixed with ethyl-linoleate and stearic acid in the ratio of each 5% (S, L-group) . The last group consisted of 10 rabbits was given the high cholesterol diet mixed with 10% of stearic acid (S-group). The animals were kept in the individual cage at the room temperature of 22±l C for 12 weeks. The body weight and the levels of the serum cholesterol and phospholipids were individually measured. At the end of 12th week of the experiment all animals were sucrificed by cutting both common carotid arteries, and the levels of cholesterol and phospholipids in the aorta and liver were estimated. The isolated paren chymatous organs were stained with hematoxylin-eosin for histological examination. Details of the procedure for estimation of crude lipids in the liver, phospholipids and cholesterol in the serum, liver and aorta were described elswhere (6).
RESULTS
Spontaneous behaviorsNo significant change in the daily food intake between the control group and the high cholesterol diet group supplemented with fatty acids was observed throughout the feed...