The anionic peptide fraction is present on the gallbladder apical epithelium and favours biliary cholesterol absorption.
OBJECTIVE
We investigated (a) in vitro and in vivo the changes of biliary mass of the anionic peptide fraction, apolipoproteinA-I, immunoglobulin-A, albumin and cholesterol over time in the excluded gallbladder and (b) in vivo the localization in the gallbladder epithelium of the anionic peptide fraction and cholesterol absorbed from bile.


METHODS
Native bile was substituted with pig bile containing radiolabeled cholesterol in the in vitro isolated intra-arterially perfused pig gallbladder (n=9) and in vivo in anestethized pigs with excluded gallbladders (n=6). The amount of cholesterol (scintillation counting) and proteins (enzyme-linked immunosorbent assay) in gallbladder bile were measured over time. The localization of the anionic peptide fraction and cholesterol absorbed from bile in the gallbladder epithelium was studied in vivo by immunohistochemistry and fluoro-phospho-imager analysis.


RESULTS
The rate of biliary cholesterol disappeared from bile was a function of the initial concentration and of the biliary mass changes over time of the anionic peptide fraction, but not of that of the other biliary proteins. The anionic peptide fraction colocalized with biliary cholesterol absorbed by the gallbladder on the apical side of gallbladder epithelial cells.


CONCLUSIONS
These data indirectly suggest that biliary anionic peptide fraction could favour biliary cholesterol absorption by the gallbladder epithelium.
Liguori
F
F
Division of Gastroenterology, Department of Clinical Medicine, University La Sapienza, Rome, Italy.
Domingo
N
N
Tebala
G
G
Ripani
C
C
De Marco
R
R
Siciliano
M
M
Attili
A F
AF
Lairon
D
D
Lafont
H
H
de la Porte
P Lechène
PL
Ginanni Corradini
S
S
D000042:Absorption; D000418:Albumins / Q000032:analysis; D000818:Animals; D016632:Apolipoprotein A-I / Q000032:analysis; D001059:Apoproteins / Q000032:analysis*; D001646:Bile / Q000737:chemistry / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000032:analysis*; D002784:Cholesterol / Q000032:analysis*; D004797:Enzyme-Linked Immunosorbent Assay; D004848:Epithelium / Q000737:chemistry / Q000378:metabolism*; D005704:Gallbladder / Q000737:chemistry / Q000378:metabolism*; D007070:Immunoglobulin A / Q000032:analysis; D066298:In Vitro Techniques; D013552:Swine
D000418:Albumins; D016632:Apolipoprotein A-I; D001059:Apoproteins; D002135:Calcium-Binding Proteins; D007070:Immunoglobulin A; C489588:anionic polypeptide fraction, human; D002784:Cholesterol