Acid-Base and Electrolyte Regulation in the Bovine Gall-Bladder Bile Model

Design: The relationship between solute and solvent in bile is important for the determination of the likelihood of precipitation of bile constituents and, therefore, gallstone formation. Materials and methods: The effect of concentration and acidification on the ionic composition of bile and calcium salt solubility was studied in 47 bovine gall bladder bile samples obtained anaerobically immediated after death. Results: Bovine bile composition is similar to that of human bile. Biliary pH showed a linear reverse relationship with sodium concentration above 200 mmol/l, a linear positive relationship with chloride and reverse linear relationship with total calcium and potassium. Osmolality remained constant across a wide range of solute concentrations. Of the bite samples with pH >7.10, 60% were supersaturated with calcium carbonate, but only 4% with calcium phosphate; there was also a positive relationship between the saturation indices for those salts and pH. Conclusions: The formation of calcium carbonate crystals which serve as a nidus for gallstone formation is favoured in alkaline bile. Bovine bile allows the integrated study of normal bile and provides a good model for the study of gait bladder bile physiology, particularly in relation to acid-base and electrolyte regulation.