Concentrating function of the gallbladder

The major effect of the gallbladder on bile composition is the removal of water and inorganic electrolytes, thereby raising the concentrations of all of the larger organic solutes. Some of the mechanisms involved in the absorptive process have been discussed previously. The luminal electronegativity, which is the result of passive ionic diffusion, may effect the distribution of electrolytes and specifically lead to elevated concentrations of potassium and calcium. Finally, the gallbladder is appreciably permeable to lipid-soluble molecules, and this may lead to gradual but significant alteration of bile composition by absorption of biliary lipids and of unconjugated bilirubin (generated, possibly, by bacterial enzymatic breakdown of conjugated bilirubin). Even some of the bile acids, particularly those conjugated with glycine or those which have undergone bacterial deconjugation, may be absorbed. The possible consequences of these gradual changes remain speculative.