Effects of UTP on Na+, Cl- and K+ transport in primary cultures from human sweat gland coils.
Extracellular ATP and UTP can increase membrane permeability in the sweat gland, but the intracellular signalling regulating the response to these agonists is poorly understood. Stimulation of Cl- transport by nucleotides has been suggested as a pharmacological therapy to improve Cl- secretion in patients with cystic fibrosis. In the present study, regulation of Na+, Cl- and K+ transport in primary cultures of cells from the secretory coil of human sweat glands was investigated by electron probe X-ray microanalysis. Stimulation with 200 microM UTP for 2 min at room temperature caused a significant increase in intracellular Na but did not affect Cl and K. After 5 min, the Na concentration was still increased, but now also a significant decrease in Cl and K was observed, indicating an increase in Cl- and K+ permeability. The effect of UTP on Cl- secretion was enhanced in Mg2+-deficient buffer, indicating that the response is elicited by the extracellular fully ionized form of UTP (UTP4+), but not by MgUTP2+. The effects of UTP were abolished in Ca2+-deficient buffer supplemented with EGTA. Alloxan, an adenylate cyclase inhibitor, did not inhibit the response to UTP. These results indicate that the membrane Cl- and K+ permeability elicited by UTP in primary coil cell cultures is Ca2+-dependent. The response to UTP did not attenuate at 8 degrees C, suggesting that it could be activated, in part, via ligand-gated ion channels. The effect of UTP was not decreased in the presence of ouabain. Pre-treatment of the cells with pertussis toxin (24 h) had minor effects on Cl- secretion activated by UTP, indicating a role for G proteins in the UTP activation of Cl- secretion.
Hongpaisan
J
J
Department of Medical Cell Biology, University of Uppsala, Sweden.
Roomans
G M
GM
D037361:Adenylate Cyclase Toxin; D002118:Calcium / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism*; D003080:Cold Temperature; D000242:Cyclic AMP / Q000494:pharmacology; D004577:Electron Probe Microanalysis; D006801:Humans; D017136:Ion Transport / Q000187:drug effects; D008274:Magnesium / Q000494:pharmacology; D008854:Microscopy, Electron; D010042:Ouabain / Q000494:pharmacology; D037342:Pertussis Toxin; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D013545:Sweat Glands / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D014544:Uridine Triphosphate / Q000494:pharmacology*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D037361:Adenylate Cyclase Toxin; D002712:Chlorides; D010566:Virulence Factors, Bordetella; D010042:Ouabain; D012964:Sodium; D000242:Cyclic AMP; D037342:Pertussis Toxin; D008274:Magnesium; D011188:Potassium; D002118:Calcium; D014544:Uridine Triphosphate