Journal of Lipid Research, Vol. 7, 372-378, May 1966
Copyright © 1966 by Lipid Research, Inc.

Turnover of cholesterol-4-¹⁴C and cholic acid-24-¹⁴C by rabbits fed a diet containing lactose

N. Iritani and W. W. Wells

Biochemistry Department, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania

Rabbits fed 0.35% of cholesterol in diets containing either 29.35% of lactose or sucrose were studied for 14 weeks. The rabbits fed lactose had higher plasma and liver cholesterol concentrations than those fed sucrose. The half-life of cholesterol was 19.0 days and 35.0 days for rabbits fed sucrose and lactose, respectively. The half-life, pool size, and daily production of deoxycholic acid were 9.7 days, 1.29 g, and 74.1 mg for rabbits fed sucrose; and 14.2 days, 1.40 g, and 49.1 mg, for those fed lactose. Cholesterol was the major neutral sterol in the feces of the rabbits fed lactose, whereas coprostanol (5-cholestan-3-ol) dominated the corresponding fraction in those fed sucrose.

The fecal steroid composition did not vary between day and night collections. No sterol esters were detected in the feces. Urinary elimination of radioactivity was less than 10% of that injected.

The "lactose effect" seems to be due to enhanced retention of steroids, the mechanism of which has not been elucidated.

Supplementary key words rabbit • diet • sucrose • lactose • turnover • cholesterol • deoxycholic acid • biosynthesis • fecal composition • intestinal microorganisms

Submitted on October 11, 1965
Accepted on January 18, 1966

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