title: The thyroid cell monolayer in culture. A tight sodium absorbing epithelium.
abstract: When cultured on collagen coated nitrocellulose filters, thyroid epithelial cells form morphologically and functionally polarized monolayers. The bioelectric parameters of these monolayers were measured after mounting in Ussing chambers; transepithelial potential (Vab), short circuit current (Isc) and transepithelial resistance were respectively 12 +/- 1 mV (apical side negative), 3.8 +/- 0.2 microA cm-2 and 3250 +/- 214 omega cm2 (mean +/- SEM, n = 75). Eighty two percent of the short circuit current was related to sodium absorption as shown by inhibition by apical amiloride (Km = 0.2 microM) and by basal ouabain (K1/2 = 0.3 microM). Amphotericin B (5-25 micrograms/ml) added to the apical bath increased Isc suggesting an apical rate-limiting step. Step by step replacement of choline by Na+ in a Na+-free medium resulted in a progressive increase in Vab and Isc with half maximal effect at 20 +/- 1 mM Na+. Thyrotropin (TSH) increased Isc and Vab in a biphasic way with a transient maximum after 5 min and a plateau after 20 min (about four times the basal level at 100 microU/ml TSH). This increase in sodium transport was also inhibited by apical amiloride. Thus, in culture, the thyroid cell monolayer behaves as a tight sodium absorbing epithelium controlled by TSH, with a rate limiting apical sodium channel as the entry mechanism and a basolateral Na+, K+-ATPase as the electromotive force.
authors.affiliation: INSERM Unité U 270 Faculté de Médecine Nord, Marseille, France.
authors.forename: C
authors.initials: C
authors.lastname: Penel
authors.forename: C
authors.initials: C
authors.lastname: Gérard
authors.forename: J
authors.initials: J
authors.lastname: Mauchamp
authors.forename: B
authors.initials: B
authors.lastname: Verrier
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000666:Amphotericin B / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002478:Cells, Cultured; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D008854:Microscopy, Electron; D010042:Ouabain / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013552:Swine; D013961:Thyroid Gland / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D013972:Thyrotropin / Q000502:physiology
chemical_list: D010042:Ouabain; D000584:Amiloride; D000666:Amphotericin B; D013972:Thyrotropin; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase