1. The effect of conjugated and unconjugated bile acids in various concentrations on the absorption of water, sodium and chloride in the proximal jejunum in man has been studied using a perfusion system incorporating a proximal occluding balloon.
2. Unconjugated cholic acid and its glycine and taurine conjugates had no significant effect on water and electrolyte absorption. Unconjugated deoxycholic acid significantly inhibited water and electrolyte absorption at 3 mm concentration and net secretion occurred at concentrations of 5 mm, 7 mm and 10 mm. Similar results were found when taurodeoxycholic and glycodeoxycholic acid solutions were used. A greater effect was noted when higher concentrations of bile acids were used.
3. Unconjugated chenodeoxycholic acid caused net water and electrolyte secretion at 3 mm concentration and this effect became more marked with higher bile acid concentrations. Inhibition of absorption also occurred with taurochenodeoxycholic acid in a concentration of 3 mm and net secretion occurred at a concentration of 10 mm.
4. The results show that dihydroxy bile acids, conjugated or unconjugated, inhibit water and electrolyte absorption in the proximal jejunum in low concentration and cause net secretion in high concentration.