CELL-SPECIFIC AND REGION-SPECIFIC EXPRESSION OF BILIARY GLYCOPROTEIN AND ITS MESSENGER-RNA IN NORMAL HUMAN COLONIC MUCOSAL

The localization of biliary glycoprotein (BGP) and its mRNA in normal colonic mucosa was studied by immunohistochemistry and in situ hybridi zation. BGP mRNA was confined to columnar epithelial cells and express ed abundantly in the superficial mature cells and at low levels in dif ferentiating cells in the upper crypts. Epithelial expression of BGP c oincided with that of BGP mRNA. Ultrastructurally, BGP was localized t o microfilaments of the fuzzy coat of the columnar cells at the lumina l surface and the upper crypts. Additionally, BGP was found in cryptal caveolated cells. The results are consistent with primary transcripti onal regulation of BGP production and suggest that BGP synthesis is co ntrolled by the degree of cytodifferentiation. The fuzzy-coat localiza tion of BGP implies a role in nonspecific defense mechanisms against p athogens.