Jf. Madrid et al., SUBCELLULAR CHARACTERIZATION OF GLYCOPROTEINS IN THE PRINCIPAL CELLS OF HUMAN GALLBLADDER - A LECTIN CYTOCHEMICAL STUDY, Histochemistry, 101(3), 1994, pp. 195-204
Gallbladder mucus is mainly composed of glycoproteins, which seem to p
lay a critical role in cholesterol nucleation during gallstone formati
on. The biosynthetic pathway and sequential processing as well as the
characterization of the oligosaccharide sidechains of human gallbladde
r secretory glycoproteins have not been completely defined. The aim of
the present study is the subcellular characterization of the glycopro
teins in the principal cells of human gallbladder. Principal cells of
normal human gallbladder were studied by means of a variety of cytoche
mical techniques, including lectin histochemistry, enzyme and chemical
treatments, immunocytochemistry and lectin-gold technology. Fucose, g
alactose, N-acetylglucosamine, N-acetylgalactosamine and N-acetylneura
minic acid residues were detected in mucous granules, Golgi apparatus
and apical membrane of principal cells. Mannose residues were only obs
erved in dense bodies. Oligosaccharide side-chains of the glycoprotein
s contained in the biliary mucus are synthesized in the Golgi apparatu
s of the principal cells of the gallbladder epithelium and are also co
ntained in the mucous granules of these cells. Terminal N-acetylneuram
inic acid(alpha 2-3)galactose(beta 1-3)N-acetylgalactosamine, N-acetyl
neuraminic acid(alpha 2-3)galactose(beta 1-4)N-acetylglucosamine and g
alactose(beta 1-4)N-acetylglucosamine sequences are contained in the o
ligosaccharide chains of gallbladder mucus glycoproteins. The dense bo
dies detected in the cytoplasm of the principal cells contained N-link
ed glycoproteins. Mucin-type O-linked glycoproteins were the main comp
onents of the mucous granules although some N-linked chains were also
detected.