Evidence of hydrogen ion secretion from the human gall bladder in vitro

Gall bladder bile is more acid that hepatic bile and this has been attributed to bicarbonate absorption by the gall bladder epithelium. The aim of this study was to investigate in vitro the acid base changes that occur across the human gall bladder mucosa. Fresh gall bladder tissue was obtained at cholecystectomy and placed in an Ussing Chamber and perfused with Ringer-Krebs glucose bicarbonate solution. The viability of the gall bladder was assessed by measuring the potential differences across the epithelium and by the morphology of the epithelial cells at the end of the experiments. Aliquots from the solutions were taken at two, 45 and 70 minutes and pCO2, hydrogen ion and bicarbonate concentrations were measured. In the mucosal side of the chamber a consistent and significant decrease was observed from two minutes to 70 minutes in bicarbonate concentration while pCO2 and hydrogen ion concentrations significantly increased. The degree of inflammation correlated well with the ability for acidification, the more inflamed the tissue the less its ability to acidify. When the gall bladder was exposed to amiloride or sodium free solution acidification was abolished in the mucosal side. When tissue metabolism was irreversibly inhibited by exposure to formaldehyde, hydrogen ion concentration and pCO2 were significantly decreased in the mucosal side of the chamber compared with the viable gall bladder. The human gall bladder is capable of secreting acid and this may be an important mechanism for preventing calcium precipitation and gall stone formation.