Absorption of 7-ketolithocholic acid in rat jejunum, ileum and colon.

7-Ketolithocholic acid is a bile acid which is formed in the intestine of man by bacterial oxidation of chenodeoxycholic acid and ursodeoxycholic acid. In contrast to deoxycholic acid and lithocholic acid 7-ketolithocholic acid after its intestinal absorption may be reduced in the liver to chenodeoxycholic acid or ursodeoxycholic acid. In the present study absorption of 7-ketolithocholic acid in jejunum, ileum, and colon was measured. When 7-ketolithocholic acid was perfused with a concentration of 0.025 mmol/l the absorption in the jejunum was 6.2 +/- 0.9 nmol/cmxh (mean +/- SD), in the ileum 8.1 +/- 0.2 nmol/cmxh, and in the colon 11.2 +/- 1.7 nmol/cmxh. The absorption of 7-ketolithocholic acid in jejunum, ileum, and colon was equal to the absorption of ursodeoxycholic and chenodeoxycholic acid. The equal absorption rates of 7-ketolithocholic, ursodeoxycholic, and chenodeoxycholic acid indicate, that substitution of the 7-hydroxyl group by the 7-keto group has no influence on the intestinal absorption of bile acids. The excellent colonic absorption of 7-ketolithocholic acid demonstrates, that not only the small intestine but also the colon contributes to the enterohepatic circulation of bile acids.