Activation of Ca(2+)-dependent K+ and Cl- currents by UTP and ATP in CFPAC-1 cells.
Activation of Cl- and K+ conductances by nucleotide receptor-operated mobilization of intracellular Ca2+ was investigated in CFPAC-1 cells with the perforated-patch technique. Adenosine 5'-triphosphate (ATP) and uridine 5'-triphosphate (UTP) caused a dose-dependent fast and transient membrane hyperpolarization. UTP was more effective than ATP. In voltage-clamped cells, two currents with different ionic permeability and kinetics were activated by the nucleotides. The first one was carried by Cl- ions, peaked in the first few seconds after addition of nucleotides, and lasted for 1 +/- 0.3 min. Its amplitude was about 2.7 nA at -100 mV with 100 mumol/l of either ATP or UTP. The second current was carried by K+ ions and was blocked by Cs+. This current peaked more slowly and had a mean duration of 4.6 +/- 0.7 min. Its amplitude was 0.9 nA and 0.5 nA at -20 mV with 100 mumol/l UTP and ATP, respectively. Activation of the nucleotide receptor caused a transient increase in intracellular Ca2+ concentration ([Ca2+]i) that was similar in the presence or absence of extracellular Ca2+. The ED50 for UTP was 24 mumol/l and that for ATP was 94 mumol/l. Depletion of the inositol 1,4,5-trisphosphate-sensitive Ca2+ store by thapsigargin prevented both the nucleotide-induced [Ca2+]i increase and the activation of membrane currents. Addition of 2 mmol/l Ca2+ to thapsigargin-treated cells produced a sustained increase of Cl- and K+ currents, which was reversed by Ca2+ removal. The present study demonstrates that CFPAC-1 cells respond to nucleotide receptor activation with a transient increase in [Ca2+]i that stimulates Ca(2+)-dependent Cl- and K+ currents.(ABSTRACT TRUNCATED AT 250 WORDS)
Galietta
L J
LJ
Laboratorio di Genetica Molecolare, Istituto Giannina Gaslini, Genova, Italy.
Zegarra-Moran
O
O
Mastrocola
T
T
Wöhrle
C
C
Rugolo
M
M
Romeo
G
G
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D018118:Chloride Channels / Q000187:drug effects / Q000378:metabolism*; D003550:Cystic Fibrosis / Q000378:metabolism; D004594:Electrophysiology; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D016257:Fura-2; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D010183:Pancreatic Ducts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D014544:Uridine Triphosphate / Q000494:pharmacology*
D018118:Chloride Channels; D015221:Potassium Channels; D013729:Terpenes; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D000252:Calcium-Transporting ATPases; D002118:Calcium; D016257:Fura-2; D014544:Uridine Triphosphate