Chloride conductance of apical membrane in cultured porcine thyroid cells activated by cyclic AMP.
The thyroid epithelium transports fluid bidirectionally using active transport of Na+ ions from apical to basal poles and active transport of Cl- in the reverse direction. In these studies we sought evidence for cyclic AMP activated Cl- channels on the apical membranes of thyroid cells in monolayer culture. A Cl(-)-dependent basal-positive short-circuit current (ISC) was demonstrated in bicameral chambers after blocking Na+ transport with phenamil, and responded to prostaglandin (PG) E2 with a spike of 5-10 min duration followed by a plateau. The onset of the spike coincided with an increase in the conductance of the epithelium. Application of an external Cl- concentration gradient, by replacing the medium in the apical compartment with Cl(-)-free medium, resulted in an increase in ISC after, but not before, addition of PGE2. Forskolin and thyroid-stimulating hormone (TSH), but not A23187, also stimulated Cl- transport. In conjunction with previous observations that Cl- transport was mediated by a bumetanide-sensitive NaKCl2 symporter on the basal membrane, these observations indicated the presence of a cyclic AMP activated Cl- conductance in the apical membrane of thyroid cells.
Armstrong
J W
JW
Department of Physiology and Pharmacology, University of Queensland, Brisbane, Australia.
Cragoe
E J
EJ
Bourke
J R
JR
Huxham
G J
GJ
Manley
S W
SW
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002352:Carrier Proteins / Q000187:drug effects / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D018118:Chloride Channels; D002712:Chlorides / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology*; D015232:Dinoprostone / Q000494:pharmacology; D004553:Electric Conductivity; D008565:Membrane Proteins / Q000187:drug effects* / Q000378:metabolism; D028021:Sodium-Potassium-Chloride Symporters; D013552:Swine; D013961:Thyroid Gland / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013972:Thyrotropin / Q000494:pharmacology
D002352:Carrier Proteins; D018118:Chloride Channels; D002712:Chlorides; D008565:Membrane Proteins; D028021:Sodium-Potassium-Chloride Symporters; D005576:Colforsin; D000001:Calcimycin; D013972:Thyrotropin; D000242:Cyclic AMP; D015232:Dinoprostone