Regulation of cholinesterase activity by cholinergic stimulation in swine tracheal epithelium

The present study investigated the distribution of cholinesterases (ChEs) and their activity regulated by cholinergic stimulation in swine trachea. Results showed that ACh‐induced tracheal smooth muscle contraction was gradually decreased in the presence of epithelium, but the contractile response to carbachol was not influenced. Furthermore, the inhibitory action of epithelial presence on ACh‐elicited muscle contractile response was reversed by AChE inhibitor and associated with the expression of AChE. The distributions of AChE in trachea were observed and its activity was increased by ACh stimulation. Additionally, ACh enhanced the expressions of AChE and BChE in tracheal slices and primary cultures derived from tracheal epithelium. Both of AChE and BChE activities in the release and cell extract from primary cultured tracheal epithelia were also increased by ACh, whereas the protein levels of AChE were not altered. The muscarinic receptor antagonists blocked the ACh‐induced increases in AChE activity. Alternatively, the nicotinic receptor agonists inhibited the epithelial AChE and BChE activities, which were recovered by α7 nicotinic receptor antagonist α‐bungarotoxin. In conclusion, the distribution of ChEs observed in airways is unrelated to the neuronal location, whereas the ChE activity is modulated by cholinergic stimulation.