Bile acids are not equally damaging to the gastric mucosa

Surgeons are aware that some patients with bile reflux into the stomach develop gastritis, whereas others do not. A possible explanation for this observation is that some bile acids damage the gastric mucosa more than others. Experiments were undertaken to compare the effects of four different bile acids on the gastric mucosa of dogs. Three dogs were prepared with Heidenhain pouches, each pouch being drained by two Gregory cannulas. The pouches were perfused with isotonic acid test solutions (ATSs) via a recirculating system incorporating an autotitrator and pH stat to measure acid fluxes. Potential difference (PD) across the gastric mucosa was measured by usual methods. The dogs were studied awake, standing in Pavlov slings, after an overnight fast. Two series of experiments were performed. In the first series, pouch acid loss and potential difference were measured at 10 minute intervals for 1 hour, in the control state and then with 5-, 10-, and 20 mM concentrations of bile salt in 10mM HCl ATSs made isotonic with NaCl. The sodium salts of taurodeoxycholate (pKa 1.9) and taurocholate (pKa 1.9) reduced PD and increased hydrogen ion back diffusion at pH 2. The unconjugated sodium salts of cholate (pKa 5.0) and deoxycholate (pKa 5.3) had no effect on PD or acid back diffusion at pH 2. When the gastric mucosa was exposed to bile salts at pH 7, the unconjugated bile salts, cholate and deoxycholate, both reduced PD and increased acid back diffusion. The outcome of bile reflux into the stomach may depend on the individual bile salts refluxed and on the pH of luminal exposure.