Cl - secretion induced by 5-hydroxytryptamine and calcitonin gene-related peptide in rat tracheal epithelia

Abstract

The effects of 5-hydroxytryptamine (5-HT) and calcitonin gene-related peptide (CGRP), which are colocalized in nerve terminals in the airway, on Cl- secretion in rat tracheal epithelia were tested. Short-circuit current (Isc) was measured after rat tracheal epithelial monolayers were cultured on porous filters. In rat tracheal monolayers 5-HT and CGRP increased Isc upon addition to the serosal compartment, in a dose-dependent manner with EC50 values at 5 micromol/l and 5 nmol/l, respectively. The responses were dependent on the presence of Cl- in the bathing solution and were inhibited by 100 micromol/l bumetanide. When 5-HT or CGRP was added after the administration of forskolin, the responses were not observed. 5-HT and CGRP increased the intracellular cAMP concentration. Low-Ca2+ buffer (0.1 mmol/l) and pretreatment with BAPTA/AM (10 micromol/l), thapsigargin (1 micromol/l) or indomethacin (10 micromol/l) did not affect the responses to 5-HT and CGRP. The 5-HT-induced response was not inhibited by 5-HT2 and/or 5-HT4 antagonists. These results indicate that in the rat tracheal epithelia 5-HT and CGRP increase Cl- secretion by an increase in intracellular cAMP concentration via direct activation of basolateral receptors, and that the response to 5-HT is not mediated via 5-HT4 receptors.

5-hydroxytryptamine strongly inhibits fluid secretion in guinea pig pancreatic duct cells

“…In the guinea pig distal colon, 5-HT at 0.1-1 µM stimulated Cl -transport via cholinergic nerves (21,22). Direct stimulation of epithelial Cl -transport by 5-HT was observed at 0.05-1 µM in rat choroid plexus (23), at 1-100 µM in rat trachea (24), and at 0.1-1 µM in rat epididymis (25).…”

Serotonin via 5‐HT1B and 5‐HT2B receptors stimulates anion secretion in the rat epididymal epithelium

“…5‐Hydroxytryptamine (5‐HT) is widely distributed in the vertebrate and is important in controlling gastrointestinal motility, contraction of smooth muscle, vascular constriction and dilatation, microvascular permeability, platelet aggregation, nociception, and excitation and inhibition of neurons in the central nervous system. It has also been reported that 5‐HT may affect the secretory processes in the airway (Jung et al 1997), cornea (Marshall & Klyce, 1984), ileum (Borman & Burleigh, 1993; Franks et al 1996), jejunum (Hardcastle et al 1981), colon (Sidhu & Cooke, 1995) and gallbladder (Donowitz et al 1980).…”