AJP - Gastrointestinal and Liver Physiology, Vol 271, Issue 3 410-G414, Copyright © 1996 by American Physiological Society
Bidirectional transport of cholesterol between gallbladder epithelial cells and model bile
A. Hayashi and S. P. Lee
Department of Medicine, Veterans Affairs Medical Center, Seattle, Washington, USA.
Lipids in hepatic bile may be modified by the gallbladder epithelium. The
purpose of this study was to demonstrate a bidirectional exchange of
cholesterol between biliary lipid carriers and gallbladder epithelial cells
and to determine the factors regulating this cholesterol transfer.
Gallbladder epithelial cells were cultured to confluent monolayers, their
membranes were labeled with endogenously synthesized [14C]cholesterol, and
the cells were incubated with model bile introduced into the apical
membrane compartment. Similarly, model bile with different lipid
composition containing [3H]cholesterol was incubated with the unlabeled
monolayers. We found that cholesterol in the apical membrane bilayer of the
epithelial cells exchanged readily with that in bile, but only in the
presence of bile salts. The rate of exchange is dependent on the
concentration and species of bile salts. The net gain of cholesterol
(absorption) or net loss of cholesterol (cytotoxicity) exhibited by the
epithelial cells was regulated by the thermodynamic stability of
cholesterol and the detergent effect of mixed micelles in bile. It is also
possible that the physicochemical composition of lipids in bile may modify
the cellular function of the gallbladder epithelium.
