title: Bioelectric properties of fetal alveolar epithelial monolayers.
abstract: To investigate the bioelectric properties on one of the cell types that line the distal lung unit, we isolated type II alveolar epithelium from 18- to 20-day gestation fetal rats (term = 22 days) and grew them on collagen-coated nitrocellulose filters. Amiloride impaired ion transport in a dose-dependent fashion (10(-4) to 10(-6) M) with 10(-4) M decreasing potential difference (PD) (mean +/- SE, 2.0 +/- 0.49 to 0.9 +/- 0.26 mV, P less than 0.01, lumen negative) and short-circuit current (Isc) (7.0 +/- 1.0 to 2.4 +/- 0.64 uA/cm2, P less than 0.01) without affecting resistance (R) (241 +/- 33 to 216 +/- 41 omega. cm2). Benzamil (10(-5) M) but not dimethylamiloride (10(-5) M) decreased Isc. Terbutaline (10(-3) M) increased PD from 1.2 +/- 0.13 to 3.3 +/- 0.40 mV (P less than 0.01), and application of amiloride (10(-4) M) after terbutaline reduced PD and Isc to less than initial base-line values. The Na(+)-K(+)-2Cl- cotransport inhibitors bumetanide (10(-4) M) and furosemide (10(-3) M) had no effect on PD and Isc either before or after terbutaline. Neither the Cl- channel blocker diphenylamine-2-carboxylate (10(-3) M) nor the Na(+)-glucose cotransport inhibitor phloridzin (10(-3) M) affected the bioelectric properties. Fetal type II alveolar epithelium in primary culture actively transport ions and, on the basis of inhibitor-agonist experiments, probably do not secrete Cl- but absorb Na+ through Na+ channels.
authors.affiliation: Department of Paediatrics, Hospital for Sick Children Research Institute, Toronto, Ontario, Canada.
authors.forename: H
authors.initials: H
authors.lastname: O'Brodovich
authors.forename: B
authors.initials: B
authors.lastname: Rafii
authors.forename: M
authors.initials: M
authors.lastname: Post
mesh_terms: D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002034:Bumetanide / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004847:Epithelial Cells; D004848:Epithelium / Q000502:physiology / Q000648:ultrastructure; D005333:Fetus; D005665:Furosemide / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D008854:Microscopy, Electron; D010042:Ouabain / Q000494:pharmacology; D010695:Phlorhizin / Q000494:pharmacology; D011650:Pulmonary Alveoli / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology; D013726:Terbutaline / Q000494:pharmacology; D062367:ortho-Aminobenzoates / Q000494:pharmacology
chemical_list: D015222:Sodium Channels; D062367:ortho-Aminobenzoates; C013407:benzamil; D002034:Bumetanide; D010042:Ouabain; D000584:Amiloride; D005665:Furosemide; C001209:fenamic acid; D012964:Sodium; D010695:Phlorhizin; D013726:Terbutaline