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Biotin Absorption by Distal Rat Intestine^1,2,

Section of Gastroenterology and Clinical Nutrition Research Unit, The University of Chicago, Chicago, IL 60637

We used the in vivo intestinal loop approach, with short (10-min) and long (3-h) incubations, to examine biotin absorption in proximal jejunum, distal ileum, cecum and proximal colon. In short-term studies, luminal biotin disappearance from rat ileum was about half that observed in the jejunum, whereas absorption by proximal colon was about 12% of that in the jejunum. In 3-h closed-loop studies, the absorption of 1.0 µM biotin varied regionally. Biotin absorption was nearly complete in the small intestine after 3 h; however, only about 15% of the dose had been absorbed in the cecum and 27% in the proximal colon after 3 h. Independent of site of administration, the major fraction of absorbed biotin was recovered in the liver; measurable amounts of radioactive biotin were also present in kidney and plasma. The results support the potential nutritional significance for the rat of biotin synthesized by bacteria in the distal intestine, by demonstrating directly an absorptive capability of mammalian large bowel for this vitamin.

KEY WORDS: • biotin • intestinal absorption • rat

¹ Portions of this work were presented at the Federation of American Societies for Experimental Biology meeting held in April, 1986, in St. Louis, MO, and have been published in abstract form [Bowman, B. B. & Rosenberg, I. H. (1986) In vivo studies of biotin absorption in distal rat intestine. Fed. Proc. 45: 584 (abs. 2503)].

² This research project was supported in part by U.S. Public Health Service Grants No. AM 15351 and No. AM26678.

³ Present address: Department of Biochemistry, Emory University School of Medicine, Woodruff Memorial Building, Atlanta, GA 30322.

⁴ Present address: USDA Human Nutrition Research Center on Aging, Tufts University, 711 Washington Street, Boston, MA 02111.

⁵ To whom correspondence and reprint requests should be addressed.

Manuscript received 28 April 1987. Revision accepted 31 August 1987.