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SummaryThe effect of soybean protein on coprostanol production and cholesterol metabolism was studied in cholesterol-fed rats.Plasma cholesterol was decreased in the soybean protein diet group compared to the casein diet group. Although coprostanol was produced more in rats fed soybean protein than in those fed casein, no difference was observed in the levels of total neutral steroids at any part of the intestine.The activity of microbial conversion from cholesterol to coprostanol was evidently high in rats fed soybean protein.The total amount of neutral steroids excreted in feces had a tendency to increase. These data seem to indicate that the increase of the unabsorbed soybean protein causes the increase of intestinal coprostanol production.

The effects of casein and soybean protein on plasma lipoproteins, apoproteins and liver lipids in cholesterol-fed rats were studied. 1) The diet composition for the standard group was (%): casein 20, corn oil 5, vitamin mix. 1, salt mix. 4, choline chloride 0.2 and corn starch to 100%. The control diet contained 0.5% of cholesterol and 0.3% of sodium cholate and 5% of lard replaced for corn oil. In rats given a control diet, the concentration of total cholesterol was higher in VLDL and LDL and lower in HDL2, and the concentration of ApoC in VLDL, ApoE, ApoA-1 and ApoC in HDL2 and ApoE in HDL3 were lower than in the animals given a standard diet. On feeding the control diet, much cholesterol and triglyceride were stored in the liver. 2) In order to investigate the effects of qualities and quantities of proteins, the diets containing 5% of lard, 0.5% of cholesterol and 0.125% of sodium cholate was used. The concentrations of serum total cholesterol was 134.7, 108.5, 95.5 and 81.6mg/dl on the diets of casein 20%, casein 40%, soybean protein 20% and soybean protein 40%, respectively. Especially in rats fed soybean protein diets the concentration of triglyceride also decreased. On the pattern of polyacrylamide gel disc electrophoresis of serum lipoproteins, the percentage of

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Effect of the diet containing high-cholestrol and high-fat was studied on aortic tunica intima in rats. The purpose of this study was to investigate diet-induced ultrastructral change of the aorta in the experimental animals by scanning and transmission electron microscopy. Male Wistar-strain rats weighing about 120g were kept for 5 months on a semi purified diet containing 5% cholesterol and 40% non-salted butter as experimental animals (cholesterol-fed rats).The other rats fed commertial laboratory ration served as control.The results were as follows: 1) By scanning electron microscopic observations, the most conspicuous ultrastructural findings in the cholesterol-fed rats were a formation of many wrinkles on the endothelial surface and change of endothelial form.In addition, numerous leukocytes and a certain number of platelets attached to the endothelial surface. 2) By transmission electron microscopic observations, it was found that fat-containing cells (so-celled foam cell) or immature type of the foam cell at subendothelium of the intima in cholesterol-fed rats. These morphologic change suggest that diet-induced hypercholesterolemia might be a factor of endothelial injury which would serve as possible initiating events in atherosclerosis.