Effect of vasoactive intestinal peptide on ion transport across dog tracheal epithelium.
Under short-circuit conditions, vasoactive intestinal peptide (VIP) did not alter net Na+ movement but selectively stimulated net Cl- secretion across dog tracheal epithelium with a high affinity (Km congruent to 10(-8) M). The increase in Cl- secretion was not different from the rise in short-circuit current (Isc). However, stimulation of Cl- secretion was not maximal, because the addition of isoproterenol (10(-6) M) to VIP-treated tissues further increased the Isc by 54%. The effect of exogenous VIP was not blocked by a combination of atropine, phentolamine, propranolol (10(-5) or 10(-6) M), or tetrodotoxin (10(-6) M). Under open-circuit conditions, VIP caused an increase in the net secretion of Cl- and Na+, but the changes did not reach statistical significance. We conclude that VIP acts directly on receptors on the surface of epithelial cells to stimulate active Cl- secretion. The abundance of VIP nerves in the submucosa suggests that VIP may be important in regulation of fluid movement across the epithelium.
D000818:Animals; D001692:Biological Transport; D002712:Chlorides / Q000378:metabolism*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D004848:Epithelium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology; D013997:Time Factors; D014132:Trachea / Q000378:metabolism*; D014660:Vasoactive Intestinal Peptide / Q000037:antagonists & inhibitors / Q000494:pharmacology*
D002712:Chlorides; D014660:Vasoactive Intestinal Peptide; D013779:Tetrodotoxin; D012964:Sodium