At. Mariassy et al., LECTIN-DETECTABLE GLYCOCONJUGATE PROFILE OF THE TRACHEAL SECRETIONS AND EPITHELIAL GLYCOCALYX IN SHEEP - EFFECT OF MUSCARINIC STIMULATION, The American review of respiratory disease, 147(6), 1993, pp. 1550-1556
Reflex mucus secretion in the airways serves a defense function that i
ncludes the binding of bacteria to mucus glycoconjugates thereby preve
nting bacterial adherence to the epithelium. We therefore compared the
lectin-detectable glycoconjugate profile of the epithelial glycocalyx
and luminal secretions under baseline conditions and after muscarinic
receptor stimulation in the sheep trachea. The sheep were intubated w
ith a double-balloon nasotracheal tube to create a tracheal chamber fo
r collection of secretions. After an initial lavage of the chamber to
clear it of secretions, the sheep received an intravenous injection of
normal saline, 0.5 mg/kg pilocarpine, or 0.5 mg/kg pilocarpine after
pretreatment with 0.2 mg/kg atropine. Tracheal lavage was repeated 2 h
later, and the sheep were then killed. An enzyme-linked lectin assay
and lectin histochemistry were used to characterize glycoconjugate res
idues in tracheal secretions and in the apical epithelial glycocalyx,
respectively. Eight different lectins were used to detect N-acetyl gal
actosamine, alpha-galactose, alpha-galactose-N-acetyl galactosamine, b
eta-galactose, beta-galactose-N-acetyl galactosamine, alpha-fucose, al
pha-glucose, alpha-mannose and alpha-(2-3)sialyl residues. After norma
l saline, reactivity was present for all glycoconjugates in secretions
and in the glycocalyx. After pilocarpine, there was a greater reactiv
ity for alpha-galactose, alpha-galactose-N-acetyl galactosamine, alpha
-mannose, alpha-(1-3)mannose, alpha-fucose, sialyl residues, and possi
bly alpha-glucose by 200 to 692% (n = 6, p < 0.05) and similar reactiv
ity for beta-galactose and beta-galactose-N-acetyl galactosamine in se
cretions; in the glycocalyx, there was greater reactivity for beta-gal
actose, beta-galactose-N-acetyl galactosamine, alpha-(1-3)mannose, and
sialyl by 209 to 700% (p < 0.05), but there were only minimal differe
nces in the other glycoconjugates. Atropine prevented all effects of p
ilocarpine. These observations suggest that the secretions and the epi
thelial glycocalyx in sheep trachea have different glycoconjugate prof
iles. Muscarinic stimulation leads to profound but different alteratio
ns in both glycoconjugate profiles, which could influence the competin
g binding of the secretions and epithelium to bacteria colonizing the
airway.