Chloride channels in the apical membrane of thyroid epithelial cells are regulated by cyclic AMP.
Porcine thyroid epithelial cells cultured as a monolayer with their apical membranes facing the medium are known to absorb Na+ and to secrete the anions Cl- and HCO3-. Chloride channels were found in the apical membrane, and displayed a reversal potential close to the resting membrane potential, linear current-voltage relationships, a conductance at physiological temperature of 6.5 pS, and a small but significant permeability to HCO3-. Stimulation of ion transport with prostaglandin E2 or 8-(4-chlorophenylthio) adenosine 3':5'-cyclic monophosphate promoted activation of Cl- channels in cell-attached patches, and excised patches were reactivated by exposure of their cytoplasmic surface to protein kinase A and ATP. Physiological temperatures were necessary for activation of Cl- channels in cell-attached patches. The channels exhibited sub-states with a conductance exactly half that of the full unit conductance, suggesting a dual-barrelled channel structure. It is concluded that the apical membrane of thyroid epithelial cells contains cyclic AMP-activated Cl- channels controlling anion transport.
Department of Physiology and Pharmacology, University of Queensland, Australia.
J R
JR
Bourke
O
O
Sand
K C
KC
Abel
G J
GJ
Huxham
S W
SW
Manley
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D018118:Chloride Channels / Q000378:metabolism*; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D015232:Dinoprostone / Q000494:pharmacology; D004848:Epithelium / Q000378:metabolism; D015640:Ion Channel Gating / Q000187:drug effects*; D017136:Ion Transport / Q000187:drug effects; D013552:Swine / Q000378:metabolism*; D013696:Temperature; D013873:Thionucleotides / Q000494:pharmacology; D013961:Thyroid Gland / Q000378:metabolism*
D018118:Chloride Channels; D013873:Thionucleotides; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; D000242:Cyclic AMP; D015232:Dinoprostone