ABSTRACT
Objective To investigate the role of osteopontin (OPN) in the pathogenesis ot cholesterol gallstone formation in bile.Methods The nucleation time of OPN in model bile and human gallbladder bile was studied by the nucleation time assay,the effect of OPN on cholesterol crystal growth in model bile was examined by the cholesterol crystal growth assay.The effect of OPN on vesicle was detected by the transmission electron microscopy in model bile and gallbladder bile; then the content of OPN and calcium were detected via the commercial kits in human bile.Results Osteopontin prolonged nucleation time in a dose dependent manner in model bile and human bile,and this effect was correlated with calcium.Compared with control group,the nucleation times were prolonged by 1.50and 1.93 times in lithogenic bile at the concentration of osteopontin 50 μg/ml and 100 μg/ml (P＜0.01),respectively. Nucleation time were prolonged by 1.17 and 1.33 times in normal bile (P＜0.01) and by 1.29 and 1.48 times in model bile (P＜0.01),respectively.The rate of cholesterol crystals growth was not influenced by calcium ions,but inhibited by osteopontin in a dose dependent manner in the model bile.Furthermore,the formation,aggregation and fusion of vesicles were delayed by osteopontin in bile samples as indicated by the transmission electron microscopy.The concentration of osteopontin [(0.53± 0.08) mg/ml vs. (0.65 ± 0.14) mg/ml,P＜0.05] and the calcium ions [ (0.71 ± 0.17) mmol/L vs. ( 0.84 ± 0.08 ) mmol/L,P ＜ 0.05 ] were lower in lithogenic bile than in control.Conclusions Osteopontin can inhibit the cholesterol gallstone formation in model and human gallbladder bile as the anti nucleating factor.