Characterization of crystallization pathways during cholesterol precipitation from human gallbladder biles: identical pathways to corresponding model biles with three predominating sequences

D Q Wang,M C Carey

doi:10.1016/s0022-2275(20)37458-7

Abstract

In model biles, five crystallization sequences are present as functions of bile salt/lecithin (egg yolk) ratio and their positions on phase diagrams are influenced by bile salt hydrophobicity, temperature, and total lipid concentration (D. Q-H. Wang and M.C. Carey. J. Lipid Res. 1996.37: 606-630). To determine whether the same pathways occur ex vivo during cholesterol precipitation from human gallbladder biles, we examined 22 cholesterol gallstone (CSI = 1.56 +/- 0.26), 4 pigment gallstone (0.69 +/- 0.06), and 4 control biles (0.85 +/- 0.22) by microscopy and lipid analytic techniques for 30 days. Temperature was varied (4-45 degrees C) to move relative compositions into adjacent pathways or supersaturated zones to test whether the same bile could be forced to crystallize in different sequences. Sequences in native bile were identical to those in model systems composed of mixed bile salts-lecithin-cholesterol mixtures, and three corresponding pathways (B, C, D; op. cit.) were observed at 37 degrees C. With increasing lecithin content, we found i) B: plate-like cholesterol monohydrate crystals appeared before arc-shaped (putatively anhydrous cholesterol) crystals which transformed via helices and tubules into plate-like crystals and no liquid crystals formed; ii) C: lamellar liquid crystals, typified by birefringent multilamellar vesicles, were detected before cholesterol monohydrate crystals, and subsequently arc, helical and tubular crystals appeared; and iii) D: precipitation of lamellar liquid crystals was followed by cholesterol monohydrate crystals and no arc crystals were detected. Added EDTA prevented calcium bilirubinate formation, but crystallization sequences in these biles were identical to those without EDTA. We conclude that i) cholesterol crystallization pathways and sequences in human gallbladder biles are identical to model biles matched for appropriate physical-chemical conditions; ii) three of the five sequences observed in model biles were found in native bile; and iii) calcium bilirubinates neither promote biliary cholesterol crystallization nor influence crystal growth.

Highlights

In model biles, five crystallization sequences are present as functions of bile salt/lecithin ratio and their positions on phase diagrams are influenced by bile salt hydrophobicity, temperature, and total lipid concentration
Positions of the pathways on phase diagrams were shown to be influenced by temperature, bile salt (BS) hydrophobicity, and total lipid concentration [TL] [5]. calcium is present in substantial concentrations in bile [6] and often precipitates as inorganic and organic salts in gallstones [7,8,9], we found that even superphysiological (5-20 mM) levels of added calcium did not influence crystal detection times nor micellar Ch solubility in model biles but were a strong crystal growth agent [5] especially at the higher concentrations
We have explored whether the crystallization pathways and sequences in human gallbladder biles agreed with the ones observed in model bile systems [5]

Summary

Introduction

Five crystallization sequences are present as functions of bile salt/lecithin (egg yolk) ratio and their positions on phase diagrams are influenced by bile salt hydrophobicity, temperature, and total lipid concentration Positions of the pathways on phase diagrams were shown to be influenced by temperature, BS hydrophobicity, and total lipid concentration [TL] [5]. calcium is present in substantial concentrations in bile [6] and often precipitates as inorganic and organic salts in gallstones [7,8,9], we found that even superphysiological (5-20 mM) levels of added calcium did not influence crystal detection times nor micellar Ch solubility in model biles but were a strong crystal growth agent [5] especially at the higher concentrations. The strategy of incubating the same bile at different temperatures showed that bile could crystallize in several sequences depending o i l the ainbient physical-chemical conditions This systematic study provides a framework for further investigation of the effects of endogenous and exogenous pro- and anticrystallizing factors on Ch crystallization from native bile

Methods

Results

Conclusion