EFFECT OF 5-HYDROXYTRYPTAMINE ON BIOELECTRIC PROPERTIES OF AIRWAY EPITHELIAL-CELLS IN CULTURE

To elucidate whether 5-hydroxytryptamine (5-HT) affects airway epithel ial electrolyte transport and, if so, what the mechanism of action is, we studied the bioelectric properties of canine cultured tracheal epi thelium under short-circuit conditions in vitro. Mucosal addition of 5 -HT dose-dependently increased short-circuit current (Isc), which was accompanied by increases in transepithelial potential difference and c ell conductance. In contrast, 5-HT had no effect on bioelectric proper ties when it was added to the submucosal side. Pretreatment of cells w ith amiloride potentiated the increase in Isc produced by 5-HT. In the presence of diphenylamine-2-carboxylate or Cl-free medium, 5-HT decre ased Isc from the baseline level. Incubation with BAPTA-AM but not dib utyryl cAMP greatly attenuated the 5-HT-induced increase in amiloride- insensitive portion of Isc. These results suggest that 5-HT inhibits N a absorption and stimulates Cl secretion across canine tracheal epithe lium and that the Cl secretion may be associated with elevation of int racellular Ca2+ contents.