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5‐Hydroxytryptamine inhibits Na absorption and stimulates C1 secretion across canine tracheal epithelial sheets
Author(s) -
TAMAOKI J.,
CHIYOTANI A.,
TAKEMURA H.,
KONNO K.
Publication year - 1997
Publication title -
clinical and experimental allergy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.462
H-Index - 154
eISSN - 1365-2222
pISSN - 0954-7894
DOI - 10.1111/j.1365-2222.1997.tb01241.x
Subject(s) - endocrinology , transepithelial potential difference , medicine , 5 ht receptor , ketanserin , receptor , bronchoconstriction , chemistry , serotonin , epithelium , ion transporter , biology , pathology , biochemistry , asthma , membrane
Summary Background 5‐Hydrozytryptamine (5‐HT) can be released from mast cells and platelets through an IgE‐dependent mechanism and may play a role in the pathogenesis of allergic bronchoconstriction. However, the effect of 5‐HT on ion transport by airway epithelium remains uncertain. Objective To determine whether 5‐HT alters electrical and ion transport properties of C1‐secreting epilhelia and, if so, what subtype of 5‐HT receptors is involved, we studied canine tracheal epithelium under short‐circuit conditions in vitro . Methods Canine tracheal mucosa was mounted in Lucite half‐chambers and the responses of short‐circuit current (lsc), transepithelial potential difference (PD) and tissue conductance (G) were measured. ln addition, ion fluxes were directly measured using 22 Na and 36 C1. Results Mucosal addition of 5‐HT caused a rapid increase in lsc, which was accompanied by the increases in PD and G, whereas submucosal 5‐HT had no effect. In the presence of amiloride, 5‐HT and its receptor agonists dose‐dependently increased lsc, with the rank order of potency being 5‐HT > α‐methyl‐5‐HT>2‐methyl‐5HT>5‐carboxamidotryptamine. The effect of 5‐HT was inhibited by ketanserin and spiperone but not by ondansetron. 5‐HT increased C1 flux from the submucosa to the mucosa with a slight inhibition of Na flux to the opposite direction. Conclusion 5‐HT inhibits airway epithelial Na absorption and stimulates C1 secretion. The latter action predominates the former and is mediated by 5‐HT 2 receptors. These effects may result in the increase in water movement toward the airway lumen.