Bidirectional ion transport in thyroid: secretion of anions by monolayer cultures that absorb sodium.
Cultured porcine thyroid cell monolayers transport Na+ in an apical-to-basal direction, resulting in the development of a basal-positive transepithelial potential difference (TEP) and the formation of domes (fluid-filled elevations of the cell layer above the culture dish substrate). Stimulation by prostaglandin E2 (PGE2) increases the magnitude of the TEP, the short-circuit current (Isc) measured in Transwell Ussing chambers, and the height of domes in cultures grown on impermeable substrates. A phenamil-resistant, PGE2-stimulated component of the Isc in Transwells and of the TEP in monolayers in conventional culture dishes was inhibitable by bumetanide, a diuretic drug that blocks NaKCl2 symporters, mediating active transport of Cl-. The rate of decrease in height of domes in cultures after addition of phenamil, presumably indicative of transport of fluid in a basal-to-apical direction, was also reduced by bumetanide. Studies with Transwells in Cl(-)-free, HCO(3-)-free or Cl(-)- and HCO(3-)-free media indicated that thyroid cells transported HCO3- as well as Cl- in a basal-to-apical direction. It was concluded that the thyroid epithelium is both sodium absorbing and anion secreting.
Armstrong
J
J
Department of Physiology and Pharmacology, University of Queensland, St Lucia, Australia.
Matainaho
T
T
Cragoe
E J
EJ
Huxham
G J
GJ
Bourke
J R
JR
Manley
S W
SW
D000042:Absorption; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D000838:Anions / Q000378:metabolism*; D001639:Bicarbonates / Q000494:pharmacology; D001692:Biological Transport; D002034:Bumetanide / Q000494:pharmacology; D002478:Cells, Cultured; D002712:Chlorides / Q000494:pharmacology; D003584:Cytological Techniques; D015232:Dinoprostone / Q000494:pharmacology; D004351:Drug Resistance; D004594:Electrophysiology; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism / Q000502:physiology; D007477:Ions; D012964:Sodium / Q000493:pharmacokinetics*; D013961:Thyroid Gland / Q000166:cytology / Q000378:metabolism* / Q000502:physiology
D000838:Anions; D001639:Bicarbonates; D002712:Chlorides; D007477:Ions; D002034:Bumetanide; C047088:phenylamil; D000584:Amiloride; D012964:Sodium; D015232:Dinoprostone