Effect of taurine and homotaurine on bile acid metabolism in dietary hyperlipidemic rats.

The effects of taurine (2-aminoethanesulfonic acid) and its homologue, homotaurine (3-aminopropanesulfonic acid), on biliary and fecal excretion of bile acids were investigated in dietary hyperlipidemic rats. Taurocholic acid was a major component in the bile of rats on laboratory chow and the ratio between glycine and taurine conjugated bile acids (G/T ratio) was 0.14. In feces, more free bile acids were present than in bile and the G/T ratio increased to 1.49. The biliary bile acid level increased approximately 2-fold in rats fed a diet containing 0.5% cholesterol and 1.0% cholic acid for 10 days. The glycine conjugated bile acid level increased approximately 7.5-fold, so that the G/T ratio was reversed to 1.17. the level of fecal bile acids increased approximately 19-fold while the G/T ratio remained at 1.43. Taurine or homotaurine (500 mg/kg/d each) was orally administered for 10 d concurrently with the cholesterol diet. Taurine suppressed elevation in the glycine conjugated bile acid level so the bile acid composition was roughly similar to that of the rats on laboratory chow and the G/T ratio became 0.06. In fecal excretion, the bile acid level increased significantly 1.2-fold over that of the control and the G/T ratio was 0.45. Homotaurine did not significantly alter the biliary bile acid level or the composition. These results indicated that taurine stimulated the excretion of bile acids, resulting in a reduction in serum cholesterol. Homotaurine did not influence bile acid metabolism.