Abstract
Intracellular free Ca2+ concentration ([Ca2-]i) and ATP play important roles in the regulation of K- channels in pulmonary artery (PA) myocytes. Previous studies have demonstrated that hypoxia and the metabolic inhibitor, 2-deoxy-D-glucose, decrease voltage-gated K- (Kv) currents [Ik(v)] and thereby depolarize PA myocytes; these effects lead to a rise in [Ca2+]i. Here, we used carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP), a protonophore that uncouples mitochondrial respiration from ATP production, to test whether the inhibition of oxidative phosphorylation affects K- channel activities in rat PA myocytes. Patch-clamp and fluorescentimaging microscopy techniques were used to measure K+ currents (Ik) and [Ca2-]i, respectively. FCCP (3-5 μM) reversibly raised [Ca2+]i in the presence and absence of external Ca2+. This effect was prevented by pretreating the cells with the membrane-permeable Ca2+ chelator, 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid-acetoxymethyl ester (BAPTA-AM). This suggests that much of the FCCP-evoked rise in [Ca2+]i was due to Ca2+ release from intracellular stores. Brief exposure to FCCP (∼2 min) reversibly enhanced IK. This augmentation was not influenced by glibenclamide, an ATP-sensitive K+ channel blocker, but was eliminated by pretreatment with BAPTA-AM. This implies that the FCCP-evoked rise in [Ca2+]; activated Ca2+-activated K+ (Kca) channels. Furthermore, in BAPTA-treated cells, longer application (≥6 min) of FCCP reversibly decreased IK(V) in PA cells bathed in Ca2--free solution. These results demonstrate that FCCP affects Kca and KV channels by different mechanisms. FCCP increases IK(Ca) by raising [Ca2+]i primarily as a result of Ca2+ release, but decreases IK(V), by a Ca2+-independent mechanism, presumably the inhibition of oxidative ATP production.
| Original language | English (US) |
|---|---|
| Journal | American Journal of Physiology - Cell Physiology |
| Volume | 270 |
| Issue number | 1 39-1 |
| State | Published - Jan 1996 |
| Externally published | Yes |
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Keywords
- Calcium-activated potassium channel
- Calcium-activated potassium current
- Carbonyl cyanide p-trifluoromethoxyphenylhydrazone
- Mitochondria
- Voltage-gated potassium channel
- Voltage-gated potassium current
ASJC Scopus subject areas
- Cell Biology
- Clinical Biochemistry
- Physiology
- Physiology (medical)
Cite this
A mitochondrial uncoupler increases KCa currents but decreases Kv currents in pulmonary artery myocytes. / Yuan, Jason; Sugiyama, Takao; Goldman, William F.; Rubin, Lewis J.; Blaustein, Mordecai P.
In: American Journal of Physiology - Cell Physiology, Vol. 270, No. 1 39-1, 01.1996.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - A mitochondrial uncoupler increases KCa currents but decreases Kv currents in pulmonary artery myocytes
AU - Yuan, Jason
AU - Sugiyama, Takao
AU - Goldman, William F.
AU - Rubin, Lewis J.
AU - Blaustein, Mordecai P.
PY - 1996/1
Y1 - 1996/1
N2 - Intracellular free Ca2+ concentration ([Ca2-]i) and ATP play important roles in the regulation of K- channels in pulmonary artery (PA) myocytes. Previous studies have demonstrated that hypoxia and the metabolic inhibitor, 2-deoxy-D-glucose, decrease voltage-gated K- (Kv) currents [Ik(v)] and thereby depolarize PA myocytes; these effects lead to a rise in [Ca2+]i. Here, we used carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP), a protonophore that uncouples mitochondrial respiration from ATP production, to test whether the inhibition of oxidative phosphorylation affects K- channel activities in rat PA myocytes. Patch-clamp and fluorescentimaging microscopy techniques were used to measure K+ currents (Ik) and [Ca2-]i, respectively. FCCP (3-5 μM) reversibly raised [Ca2+]i in the presence and absence of external Ca2+. This effect was prevented by pretreating the cells with the membrane-permeable Ca2+ chelator, 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid-acetoxymethyl ester (BAPTA-AM). This suggests that much of the FCCP-evoked rise in [Ca2+]i was due to Ca2+ release from intracellular stores. Brief exposure to FCCP (∼2 min) reversibly enhanced IK. This augmentation was not influenced by glibenclamide, an ATP-sensitive K+ channel blocker, but was eliminated by pretreatment with BAPTA-AM. This implies that the FCCP-evoked rise in [Ca2+]; activated Ca2+-activated K+ (Kca) channels. Furthermore, in BAPTA-treated cells, longer application (≥6 min) of FCCP reversibly decreased IK(V) in PA cells bathed in Ca2--free solution. These results demonstrate that FCCP affects Kca and KV channels by different mechanisms. FCCP increases IK(Ca) by raising [Ca2+]i primarily as a result of Ca2+ release, but decreases IK(V), by a Ca2+-independent mechanism, presumably the inhibition of oxidative ATP production.
AB - Intracellular free Ca2+ concentration ([Ca2-]i) and ATP play important roles in the regulation of K- channels in pulmonary artery (PA) myocytes. Previous studies have demonstrated that hypoxia and the metabolic inhibitor, 2-deoxy-D-glucose, decrease voltage-gated K- (Kv) currents [Ik(v)] and thereby depolarize PA myocytes; these effects lead to a rise in [Ca2+]i. Here, we used carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP), a protonophore that uncouples mitochondrial respiration from ATP production, to test whether the inhibition of oxidative phosphorylation affects K- channel activities in rat PA myocytes. Patch-clamp and fluorescentimaging microscopy techniques were used to measure K+ currents (Ik) and [Ca2-]i, respectively. FCCP (3-5 μM) reversibly raised [Ca2+]i in the presence and absence of external Ca2+. This effect was prevented by pretreating the cells with the membrane-permeable Ca2+ chelator, 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid-acetoxymethyl ester (BAPTA-AM). This suggests that much of the FCCP-evoked rise in [Ca2+]i was due to Ca2+ release from intracellular stores. Brief exposure to FCCP (∼2 min) reversibly enhanced IK. This augmentation was not influenced by glibenclamide, an ATP-sensitive K+ channel blocker, but was eliminated by pretreatment with BAPTA-AM. This implies that the FCCP-evoked rise in [Ca2+]; activated Ca2+-activated K+ (Kca) channels. Furthermore, in BAPTA-treated cells, longer application (≥6 min) of FCCP reversibly decreased IK(V) in PA cells bathed in Ca2--free solution. These results demonstrate that FCCP affects Kca and KV channels by different mechanisms. FCCP increases IK(Ca) by raising [Ca2+]i primarily as a result of Ca2+ release, but decreases IK(V), by a Ca2+-independent mechanism, presumably the inhibition of oxidative ATP production.
KW - Calcium-activated potassium channel
KW - Calcium-activated potassium current
KW - Carbonyl cyanide p-trifluoromethoxyphenylhydrazone
KW - Mitochondria
KW - Voltage-gated potassium channel
KW - Voltage-gated potassium current
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UR - http://www.scopus.com/inward/citedby.url?scp=0030038175&partnerID=8YFLogxK
M3 - Article
C2 - 8772460
AN - SCOPUS:0030038175
VL - 270
JO - American Journal of Physiology
JF - American Journal of Physiology
SN - 0363-6143
IS - 1 39-1
ER -