BACKGROUND: The excessive accumulation of cholesterol absorbed from bile by the gallbladder impairs its contractility and favours gallstone formation. The total low plasma and high density lipoprotein cholesterol concentrations are associated with gallstone disease. AIMS: To investigate the effect of plasma lipoproteins on gallbladder cholesterol and phosphatidylcholine absorption from bile and to establish whether cholesterol absorption is Brefeldin A-sensitive. METHODS: Gallbladder mucosa lipid absorption rates were measured using: 1) in vitro isolated intra-arterially perfused pig gallbladder model with and without plasma lipoproteins perfusing the vascular tree; 2) human gallbladder fragments mounted in Ussing chambers with plasma lipoproteins at different concentrations in the serosal side; 3) pig gallbladder fragments mounted in Ussing chambers in the presence and absence of Brefeldin A. RESULTS: Total lipoproteins and high density lipoprotein significantly increased the release of biliary cholesterol and phosphatidylcholine in plasma and significantly decreased the tissue accumulation of cholesterol absorbed from bile. The scavenger effect of plasma lipoproteins on cholesterol absorbed from bile was concentration dependent. Brefeldin A did not influence gallbladder absorption of biliary cholesterol. CONCLUSIONS: Biliary cholesterol is absorbed by gallbladder mucosa via a Brefeldin-insensitive pathway and is removed by plasma lipoproteins.
BACKGROUND: The excessive accumulation of cholesterol absorbed from bile by the gallbladder impairs its contractility and favours gallstone formation. The total low plasma and high density lipoprotein cholesterol concentrations are associated with gallstone disease. AIMS: To investigate the effect of plasma lipoproteins on gallbladder cholesterol and phosphatidylcholine absorption from bile and to establish whether cholesterol absorption is Brefeldin A-sensitive. METHODS: Gallbladder mucosa lipid absorption rates were measured using: 1) in vitro isolated intra-arterially perfused pig gallbladder model with and without plasma lipoproteins perfusing the vascular tree; 2) human gallbladder fragments mounted in Ussing chambers with plasma lipoproteins at different concentrations in the serosal side; 3) pig gallbladder fragments mounted in Ussing chambers in the presence and absence of Brefeldin A. RESULTS: Total lipoproteins and high density lipoprotein significantly increased the release of biliary cholesterol and phosphatidylcholine in plasma and significantly decreased the tissue accumulation of cholesterol absorbed from bile. The scavenger effect of plasma lipoproteins on cholesterol absorbed from bile was concentration dependent. Brefeldin A did not influence gallbladder absorption of biliary cholesterol. CONCLUSIONS: Biliary cholesterol is absorbed by gallbladder mucosa via a Brefeldin-insensitive pathway and is removed by plasma lipoproteins.