Abstract
The perforated-patch technique was used to study the response of human bronchial cells to extracellular nucleotides. ATP or UTP (100 μM) elicited a complex response consisting of a large transient membrane current increase followed by a relatively small sustained level. These two phases were characterized by different current kinetics. Throughout the transient phase (2-3 min) the membrane current (I(p)) displayed slow activation and deactivation kinetics at depolarizing and hyperpolarizing potentials respectively. At steady-state (I(s)) the relaxation at hyperpolarizing potential disappeared whereas at positive membrane potentials the current became slightly deactivating. The I(s) amplitude was dependent on the extracellular Ca2+ concentration, being completely inhibited in Ca2+-free medium. Cell preincubation with the membrane-permeable chelating agent BAPTA/AM prevented completely the response to nucleotides, thus suggesting that both I(p) and I(s) were dependent on intracellular Ca2+. The presence of a hypertonic medium during nucleotide stimulation abolished I(s) leaving I(p) unchanged. On the contrary, niflumic acid, a blocker of Ca2+-activated Cl- channels, prevented completely I(p) without reducing significantly I(s). 1,9-dideoxyforskolin fully inhibited I(s) but also reduced I(p). Replacement of extracellular Cl- with aspartate demonstrated that the currents activated by nucleotides were Cl- selective. I(p) resulted five times more Cl- selective than I(s) with respect to aspartate. Taken together, our results indicate that ATP and UTP activate two types of Cl- currents through a Ca2+-dependent mechanism.
| Original language | English |
|---|---|
| Pages (from-to) | 297-305 |
| Number of pages | 9 |
| Journal | Journal of Membrane Biology |
| Volume | 156 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - 1997 |
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Keywords
- ATP
- Bronchial epithelial cells
- Cl channels
- Cl currents
- Intracellular Ca
- Patch-clamp
- UTP
ASJC Scopus subject areas
- Biophysics
- Physiology
- Cell Biology
Cite this
Cl- currents activated by extracellular nucleotides in human bronchial cells. / Zegarra-Moran, O.; Sacco, O.; Romano, L.; Rossi, G. A.; Galietta, L. J V.
In: Journal of Membrane Biology, Vol. 156, No. 3, 1997, p. 297-305.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Cl- currents activated by extracellular nucleotides in human bronchial cells
AU - Zegarra-Moran, O.
AU - Sacco, O.
AU - Romano, L.
AU - Rossi, G. A.
AU - Galietta, L. J V
PY - 1997
Y1 - 1997
N2 - The perforated-patch technique was used to study the response of human bronchial cells to extracellular nucleotides. ATP or UTP (100 μM) elicited a complex response consisting of a large transient membrane current increase followed by a relatively small sustained level. These two phases were characterized by different current kinetics. Throughout the transient phase (2-3 min) the membrane current (I(p)) displayed slow activation and deactivation kinetics at depolarizing and hyperpolarizing potentials respectively. At steady-state (I(s)) the relaxation at hyperpolarizing potential disappeared whereas at positive membrane potentials the current became slightly deactivating. The I(s) amplitude was dependent on the extracellular Ca2+ concentration, being completely inhibited in Ca2+-free medium. Cell preincubation with the membrane-permeable chelating agent BAPTA/AM prevented completely the response to nucleotides, thus suggesting that both I(p) and I(s) were dependent on intracellular Ca2+. The presence of a hypertonic medium during nucleotide stimulation abolished I(s) leaving I(p) unchanged. On the contrary, niflumic acid, a blocker of Ca2+-activated Cl- channels, prevented completely I(p) without reducing significantly I(s). 1,9-dideoxyforskolin fully inhibited I(s) but also reduced I(p). Replacement of extracellular Cl- with aspartate demonstrated that the currents activated by nucleotides were Cl- selective. I(p) resulted five times more Cl- selective than I(s) with respect to aspartate. Taken together, our results indicate that ATP and UTP activate two types of Cl- currents through a Ca2+-dependent mechanism.
AB - The perforated-patch technique was used to study the response of human bronchial cells to extracellular nucleotides. ATP or UTP (100 μM) elicited a complex response consisting of a large transient membrane current increase followed by a relatively small sustained level. These two phases were characterized by different current kinetics. Throughout the transient phase (2-3 min) the membrane current (I(p)) displayed slow activation and deactivation kinetics at depolarizing and hyperpolarizing potentials respectively. At steady-state (I(s)) the relaxation at hyperpolarizing potential disappeared whereas at positive membrane potentials the current became slightly deactivating. The I(s) amplitude was dependent on the extracellular Ca2+ concentration, being completely inhibited in Ca2+-free medium. Cell preincubation with the membrane-permeable chelating agent BAPTA/AM prevented completely the response to nucleotides, thus suggesting that both I(p) and I(s) were dependent on intracellular Ca2+. The presence of a hypertonic medium during nucleotide stimulation abolished I(s) leaving I(p) unchanged. On the contrary, niflumic acid, a blocker of Ca2+-activated Cl- channels, prevented completely I(p) without reducing significantly I(s). 1,9-dideoxyforskolin fully inhibited I(s) but also reduced I(p). Replacement of extracellular Cl- with aspartate demonstrated that the currents activated by nucleotides were Cl- selective. I(p) resulted five times more Cl- selective than I(s) with respect to aspartate. Taken together, our results indicate that ATP and UTP activate two types of Cl- currents through a Ca2+-dependent mechanism.
KW - ATP
KW - Bronchial epithelial cells
KW - Cl channels
KW - Cl currents
KW - Intracellular Ca
KW - Patch-clamp
KW - UTP
UR - http://www.scopus.com/inward/record.url?scp=0030929145&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0030929145&partnerID=8YFLogxK
U2 - 10.1007/s002329900209
DO - 10.1007/s002329900209
M3 - Article
C2 - 9096070
AN - SCOPUS:0030929145
VL - 156
SP - 297
EP - 305
JO - Journal of Membrane Biology
JF - Journal of Membrane Biology
SN - 0022-2631
IS - 3
ER -