OBJECTIVETo assess the effect of cholesterol in bile on cholecystokinin receptor (CCK-R) in the gallbladder.

METHODSOne hundred Guinea pigs were randomly divided into four groups, 25 animals for each. The control group was fed a standard diet, and the cholesterol group fed a diet containing 2% cholesterol. After taking the 2% cholesterol diet for two weeks, the natural group persisted on the standard diet, and the treated group was perfused by traditional Chinese medicine. Serum cholecystokinin (CCK) level in the portal vein and maximal binding capacity (B(max)) and Kd of CCK-R in the gallbladder were measured in the four groups by RIA and RBA, and the concentrations of cholesterol in bile were also observed.

RESULTSCompared with the control group, after high-cholesterol feeding for two weeks, the gallbladder emptying rate [(65.83 +/- 7.32)% approximately (47.22 +/- 5.24)%] and B(max) of CCK-R [(60 +/- 27) approximately (32 +/- 13) fmol/mg protein] and in decreased fasting gallbladder volume (FV) [(0.89 +/- 0.26) approximately (1.34 +/- 0.61) cm(3)] and concentration of cholesterol [(0.44 +/- 0.11) approximately (0.60 +/- 0.13) mmol/L] in bile increased, but no change was in the serum CCK level and Kd of CCK-R in the cholesterol group. Compared with the natural group, after two-week in take of herb decoction of qingre lidan and liqi huoxue, FV [(1.27 +/- 0.60) approximately (0.90 +/- 0.27) cm(3)], RV [(0.85 +/- 0.45) approximately (0.32 +/- 0.12) cm(3)], FB [(0.92 +/- 0.35) approximately (0.73 +/- 0.21) cm(3)], RB [(0.76 +/- 0.34) approximately (0.29 +/- 0.08) cm(3)] in the treated group decreased significantly; but gallbladder emptying rate [(43.06 +/- 4.27)% approximately (67.01 +/- 6.82)%] increased significantly. The concentration of cholesterol in bile was lower in the treated group than in the natural group [(0.59 +/- 0.14) approximately (0.43 +/- 0.10) mmol/L], but no change was found in the serum CCK level. Bmax of CCK-R in the treated group increased significantly [(39 +/- 19) approximately (59 +/- 11) fmol/mg protein], Kd of CCK-R showed no significant changes between the treated group and natural group.

CONCLUSIONHigh cholesterol in gallbladder bile causes defective muscle contraction by down-regulating CCK-R in the gallbladder, so the reduction of cholesterol concentration of bile may contribute to gallbladder contraction.