ATP activates a Ca(2+)-dependent Cl- current in the rat thyroid cell line, FRTL-5.
The effect of external ATP on both the membrane potential and the transmembrane current of the thyroid cell line FRTL-5 has been investigated in the patch-clamp whole-cell recording configuration. In the resting situation the membrane potential is around -70 mV and the membrane acts like a K(+)-sensitive electrode. Application of ATP at concentrations higher than 1 microM elicited an increase in Cl- conductance, responsible for a membrane depolarization which could be blocked by preincubation with the P2-antagonist quinidine. Chelation of intracellular Ca2+ also blocked the ATP induced changes in membrane potential and Cl- current. Intracellular perfusion with inositol trisphosphate (IP3) (50 microM) also stimulated a Cl- current which mimicked the response induced by ATP. ATP is able to initiate a response in the absence of extracellular Ca2+, but also opens a Ca(2+)-influx pathway, as demonstrated by a secondary response upon Ca2+ readmission in the external medium, in the continued presence of ATP. ADP and ATP gamma S were able to mimic the ATP response, whereas AMP and adenosine were unable to elicit a Cl- current. The P2X receptor agonist alpha,beta-methyleneATP was without effect as was the P2Y receptor agonist 2-methylthio ATP. We conclude that ATP is able to elicit a large IP3-mediated Ca(2+)-dependent Cl- current and membrane depolarization via a novel P2-type purinergic receptor.
Martin
S C
SC
Physiological Laboratory, University of Liverpool, England.
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002463:Cell Membrane Permeability; D002712:Chlorides / Q000378:metabolism*; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D008564:Membrane Potentials; D051381:Rats; D013961:Thyroid Gland / Q000166:cytology / Q000378:metabolism*
D002712:Chlorides; D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate; D002118:Calcium