Calcium-dependent chloride secretion across cultures of human tracheal surface epithelium and glands.
Surface epithelium and gland cells from human trachea were cultured on porous-bottom inserts and loaded with fura 2 to permit measurement of the intracellular calcium concentration ([Ca2+]i). Short-circuit current (Isc), an index of transepithelial active ion transport, was measured on cells from the same cultures. Surface epithelial [Ca2+]i of 82 +/- 15 nM was increased transiently by isoproterenol, histamine, and bradykinin with maximal increases of 88 +/- 17, 480 +/- 149, and 978 +/- 214 nM (n = 15), respectively. Baseline [Ca2+]i in cultured gland cells of 68 +/- 11 nM was increased transiently by isoproterenol, histamine, methacholine, and bradykinin with maximal increases of 105 +/- 19, 233 +/- 47, 327 +/- 121, and 634 +/- 151 nM (n = 17-21), respectively. In both cell types, mediators that increased [Ca2+]i also increased Isc with a time course identical to the increase in [Ca2+]i. Pretreatment with the calcium chelator, 1,2-bis-(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid, acetoxymethyl ester (BAPTA-AM), had no effect on basal Isc or transepithelial resistance but markedly inhibited both the Isc and [Ca2+]i responses to agonists. Forskolin (10(-5) M), 3-isobutyl-1-methylxanthine (10(-3) M), dibutyryl adenosine 3',5'-cyclic monophosphate (10(-3) M), and 8-(4-chlorophenylthio)-cAMP (10(-3) M) had no or only trivial effects on Isc and [Ca2+]i. We suggest that mediators increase Isc across human airway epithelium by activating Ca-dependent basolateral K channels, resulting in hyperpolarization and an increased driving force for Cl exit through apical membrane Cl channels.
Cystic Fibrosis Research Center, University of California, San Francisco 94143.
M
M
Yamaya
T
T
Ohrui
W E
WE
Finkbeiner
J H
JH
Widdicombe
D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004594:Electrophysiology; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D008854:Microscopy, Electron; D009092:Mucous Membrane / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D014132:Trachea / Q000166:cytology / Q000378:metabolism* / Q000502:physiology
D002712:Chlorides; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; D000242:Cyclic AMP; D002118:Calcium