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Laboratory of Nutritional Biochemistry, Department of Agricultural Chemistry, Faculty of Agriculture, Hokkaido University, Kita-9, Nishi-9, Sapporo 060, Japan
The contribution of enterohepatic circulation of cholesterol and bile acids in the hypocholesterolemic activity of soybean protein isolate (SPI) was compared with the activity of casein. Intact, sham-operated, jejunectomized or ileectomized adult rats were fed a cholesterol-free, purified diet containing either 20% casein or 20% SPI for 7 or 10 d. For the subsequent 7 d the diets were reversed. In intact rats the plasma cholesterol concentration (p-chol) was significantly higher when the casein diet was fed than when the SPI diet was fed. Within 3 d after the diet cross-over, p-chol in each group of intact rats reached rapidly the same level as that in its previous counterpart. These rapid inherent responses of p-chol to the casein and SPI diets remained unchanged even when the jejunum or the ileum was resected, and p-chol in jejunectomized or ileectomized rats was similar to that found in sham-operated rats. The extent of the change in p-chol induced by exchanging dietary proteins was almost the same among intact, shamoperated, jejunectomized and ileectomized rats. These findings indicate that the interruption of enterohepatic circulation of cholesterol and bile acids is not the major factor involved in the differential effects of dietary proteins on p-chol.
KEY WORDS: plasma cholesterol dietary protein ileal resection jejunal resection rats
Manuscript received 16 December 1986. Revision accepted 26 May 1987.