Taurine conjugate of 3 alpha,6 beta,7 beta-trihydroxy-5 beta,22-cholen-24-oic acid (tauro-delta 22-beta-muricholate): the major bile acid in the serum of female rats treated with alpha-naphthylisothiocyanate and its secretion by liver slices.

Abstract

The taurine conjugate of 3 alpha,6 beta,7 beta-trihydroxy-5 beta,22-cholen-24-oic acid (tauro-delta 22-beta-muricholate) has been identified in the serum of female rats treated with alpha-naphthylisothiocyanate. Using a high performance liquid chromatographic/enzymatic method for measurement of bile acids, tauro-delta 22-beta-muricholate was the predominant bile acid in the serum of female Fischer 344 rats treated for 3 days with alpha-naphthylisothiocyanate. Other significant changes in concentrations of serum bile acids included increases in tauro-alpha-muricholate, tauro-beta-muricholate, taurocholate, taurochenodeoxycholate, and several unknown bile acids. The formation of tauro-delta 22-beta-muricholate was examined in vitro using liver slices from control rats and rats treated with alpha-naphthylisothiocyanate. Slices were incubated for 7 h in William's E medium containing no bile acids or 25 mumol/l of one of the following: beta-muricholate, tauro-beta-muricholate, or cholate. Tauro-delta 22-beta-muricholate was secreted by slices from control and treated rats and the rate was increased significantly by the addition of beta-muricholate (2.9-5.6-fold) but not tauro-beta-muricholate or cholate to the medium. Tauro-delta-beta-muricholate was formed by liver slices from endogenous precursors and from exogenous beta-muricholate. Pretreatment of rats with alpha-naphthylisothiocyanate did not alter total secretion rates but those of some important individual bile acids were affected. Because of the increased secretion of tauro-delta-beta-muricholate by liver slices with the addition of beta-muricholate to the medium, the liver may be the primary site of formation for this unsaturated bile acid.