Difference in enzymatic sulfation of bile acids between the mouse and rat

Species difference in bile acid-sulfotransferase (BAST) activity was studied between the mouse and rat. Cytosol fractions of the liver, kidney, small intestine and large intestine were incubated with bile acids and 3' phosphoadenosine-5'-phosphosulfate. The mouse liver showed BAST activity for lithocholic acid, taurolithocholic acid and taurochenodeoxycholic acid, whereas the rat liver and kidney had the activity for taurodeoxycholic acid in addition to these compounds. The highest activities were found in the mouse liver and rat kidney. The mouse small intestine showed weak activity only for lithocholic acid. No activity was found in other organs. BAST was inactive towards taurocholic acid, 7 alpha- or 12-monohydroxy-5 beta-cholanoic acid. Optimal pH of liver BAST in the two species was different from that of the rat kidney. BAST of the mouse liver showed the highest activity without addition of Mg2+, whereas that of the rat liver and kidney showed enhancement by exogenous Mg2+. These results indicated that the distribution and characteristics of mouse BAST was different from rat BAST. Such difference should be reminded in any animal study involving the two species.