cAMP-induced changes of apical membrane potentials of confluent H441 monolayers.
We recorded apical membrane potentials (Va) of H441 cells [a human lung cell line exhibiting both epithelial Na+ (ENaC) and CFTR-type channels] grown as confluent monolayers, using the microelectrode technique in current-clamp mode before, during, and after perfusion of the apical membranes with 10 microM forskolin. When perfused with normal Ringer solution, the cells had a Va of -43 +/- 10 mV (means +/- SD; n = 31). Perfusion with forskolin resulted in sustained depolarization by 25.0 +/- 3.5 mV (means +/- SD; n = 23) and increased the number, open time, and the open probability of a 4.2-pS ENaC. In contrast to a previous report (Jiang J, Song C, Koller BH, Matthay MA, and Verkman AS. Am J Physiol Cell Physiol 275: C1610-C1620, 1998), no transient hyperpolarization was observed. The forskolin-induced depolarization of Va was almost totally prevented by pretreatment of monolayers with 10 microM amiloride or by substitution of Na+ ions in the bath solution with N-methyl-d-glucamine. These findings indicate that cAMP stimulation of Na+ influx across H441 confluent monolayers results from activation of an amiloride-sensitive apical Na+ conductance and not from Va hyperpolarization due to Cl- influx through CFTR-type channels.
Lazrak
Ahmed
A
Department of Anesthesiology, University of Alabama at Birmingham, Birmingham, AL 35205-3703, USA.
Matalon
Sadis
S
D000584:Amiloride / Q000494:pharmacology; D018929:Cell Culture Techniques / Q000379:methods; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology*; D002712:Chlorides / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000187:drug effects / Q000502:physiology; D053503:Epithelial Sodium Channels; D005905:Glyburide / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D008168:Lung / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D020545:Respiratory Mucosa / Q000187:drug effects / Q000502:physiology; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology
C505032:CFTR protein, human; D002712:Chlorides; D053503:Epithelial Sodium Channels; D015222:Sodium Channels; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005576:Colforsin; D000584:Amiloride; D000242:Cyclic AMP; D005905:Glyburide