Electrical potential differences in the biliary tree.

Abstract

Abstract 1. 1. Electrical potential differences (p.d.'s) have been measured between the major bile ducts and blood (or vascular perfusion fluid) in perfused guinea pig livers and in livers of unanesthetized dogs. The bile duct lumen was always electrically negative by 2 to 23 mV. 2. 2. In the absence of the hormone secretin larger p.d.'s were correlated with higher bile concentrations of Na + , K + , and bile acid anions and with lower concentrations of Cl − and HCO 3 − . In taurocholate choleresis the p.d. either increased, decreased, or remained unchanged, mirroring changes in bile composition. 3. 3. Secretin choleresis was associated with an increased duct-negative p.d. in the dog. 4. 4. Calculation from the Nernst equation that K + in bile is at equilibrium but that Na + and Cl − concentrations are lower than equilibrium values. 5. 5. These results suggest that distal reabsorption in the biliary tree involved active absorption of both Na + and Cl − , possibly by a coupled, electrically neutral pump; that the hormone secretin activates an active anion secretory mechanism; and that the p.d. in the absence of secretin is simply an NaCl (or NaCl-NaHCO 3 ) diffusion potential.