Counter-ion binding by bile acid solutions.

The binding of Ca2+ to micelles of glycine and taurine bile acid conjugates was studied using a Ca2+-specific electrode. An investigation of the effect of buffer concentration, pH, added electrolyte and lecithin was also performed. The results indicate that the binding of Ca2+ to bile salt micelles is dependent on the number of hydroxyl groups on the steroid nucleus and on the nature of the head conjugating group, namely, glycine or taurine. It is speculated that the binding of Ca2+ to bile salt micelles may act as one mechanism to lower Ca2+ activity in bile and, thus, reduce its tendency to precipitate as insoluble calcium salts and further growth into gallstones.