Abstract
To explore possible mechanisms underlying hypoxia-induced pulmonary vasoconstriction, the effect of hypoxia on outward K+ current (I(out)) was evaluated in primary cultured rat pulmonary (PA) and mesenteric (MA) arterial smooth muscle cells using the whole cell patch-clamp technique. When the cells were bathed in standard physiological salt solution and the patch pipettes contained Ca2+-free media with 10 mM ethylene glycol-bis(β- aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), virtually all of the I(out), including both the rapidly inactivating component (I(rt)) and the steady-state (noninactivating) component (I(ss)), was mediated by voltage- gated K+ channels. Reduction of O2 tension in the bath solution from 155 Torr to <74 Torr with sodium dithionite reversibly inhibited both I(rt) and I(ss) in PA myocytes, but not in MA myocytes. The hypoxia-sensitive I(ss) was activated at about -50 mV; thus, some of the channels responsible for this current may be open at the resting membrane potential (-40 ± 1 mV) of PA cells used in this study. Hypoxia also significantly depolarized PA cells bathed in PSS (1.8 mM Ca2+) from -40.7 ± 1.3 to -24.0 ± 2.4 mV, and PA cells bathed in Ca2+-free PSS (0.1 mM EGTA) from -38.4 ± 1.3 to -26.1 ± 3.9 mV. The hypoxia-induced inhibition of I(out) in PA cells was accompanied by an apparent increase in inward Ca2+ current. Removal of extracellular Ca2+ and addition of 2 mM EGTA to the bath solution while maintaining a Ca2+-free intracellular solution with 10 mM EGTA in the pipette (to prevent Ca2+-activated K+ channels from opening) did not preclude the hypoxia- induced inhibition of I(out) in PA cells. These data indicate that hypoxia attenuates voltage-gated K+ channel activity in PA cells but not in MA cells. The mechanism by which hypoxia inhibits I(out) is not known, but might be related to inhibition of oxidative metabolism. This inhibition of I(out) depolarizes the PA cells. By secondarily opening voltage-gated Ca2+ channels and promoting Ca2+ entry, the block of these K+ channels might be responsible for initiating hypoxia-induced pulmonary vasoconstriction.
| Original language | English (US) |
|---|---|
| Journal | American Journal of Physiology - Lung Cellular and Molecular Physiology |
| Volume | 264 |
| Issue number | 2 8-2 |
| State | Published - 1993 |
| Externally published | Yes |
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Keywords
- hypoxia
- patch- clamp technique
- potassium channel
- pulmonary arterial smooth muscle cells
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine
- Cell Biology
- Physiology
Cite this
Hypoxia reduces potassium currents in cultured rat pulmonary but not mesenteric arterial myocytes. / Yuan, Jason; Goldman, W. F.; Tod, M. L.; Rubin, L. J.; Blaustein, M. P.
In: American Journal of Physiology - Lung Cellular and Molecular Physiology, Vol. 264, No. 2 8-2, 1993.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Hypoxia reduces potassium currents in cultured rat pulmonary but not mesenteric arterial myocytes
AU - Yuan, Jason
AU - Goldman, W. F.
AU - Tod, M. L.
AU - Rubin, L. J.
AU - Blaustein, M. P.
PY - 1993
Y1 - 1993
N2 - To explore possible mechanisms underlying hypoxia-induced pulmonary vasoconstriction, the effect of hypoxia on outward K+ current (I(out)) was evaluated in primary cultured rat pulmonary (PA) and mesenteric (MA) arterial smooth muscle cells using the whole cell patch-clamp technique. When the cells were bathed in standard physiological salt solution and the patch pipettes contained Ca2+-free media with 10 mM ethylene glycol-bis(β- aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), virtually all of the I(out), including both the rapidly inactivating component (I(rt)) and the steady-state (noninactivating) component (I(ss)), was mediated by voltage- gated K+ channels. Reduction of O2 tension in the bath solution from 155 Torr to <74 Torr with sodium dithionite reversibly inhibited both I(rt) and I(ss) in PA myocytes, but not in MA myocytes. The hypoxia-sensitive I(ss) was activated at about -50 mV; thus, some of the channels responsible for this current may be open at the resting membrane potential (-40 ± 1 mV) of PA cells used in this study. Hypoxia also significantly depolarized PA cells bathed in PSS (1.8 mM Ca2+) from -40.7 ± 1.3 to -24.0 ± 2.4 mV, and PA cells bathed in Ca2+-free PSS (0.1 mM EGTA) from -38.4 ± 1.3 to -26.1 ± 3.9 mV. The hypoxia-induced inhibition of I(out) in PA cells was accompanied by an apparent increase in inward Ca2+ current. Removal of extracellular Ca2+ and addition of 2 mM EGTA to the bath solution while maintaining a Ca2+-free intracellular solution with 10 mM EGTA in the pipette (to prevent Ca2+-activated K+ channels from opening) did not preclude the hypoxia- induced inhibition of I(out) in PA cells. These data indicate that hypoxia attenuates voltage-gated K+ channel activity in PA cells but not in MA cells. The mechanism by which hypoxia inhibits I(out) is not known, but might be related to inhibition of oxidative metabolism. This inhibition of I(out) depolarizes the PA cells. By secondarily opening voltage-gated Ca2+ channels and promoting Ca2+ entry, the block of these K+ channels might be responsible for initiating hypoxia-induced pulmonary vasoconstriction.
AB - To explore possible mechanisms underlying hypoxia-induced pulmonary vasoconstriction, the effect of hypoxia on outward K+ current (I(out)) was evaluated in primary cultured rat pulmonary (PA) and mesenteric (MA) arterial smooth muscle cells using the whole cell patch-clamp technique. When the cells were bathed in standard physiological salt solution and the patch pipettes contained Ca2+-free media with 10 mM ethylene glycol-bis(β- aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), virtually all of the I(out), including both the rapidly inactivating component (I(rt)) and the steady-state (noninactivating) component (I(ss)), was mediated by voltage- gated K+ channels. Reduction of O2 tension in the bath solution from 155 Torr to <74 Torr with sodium dithionite reversibly inhibited both I(rt) and I(ss) in PA myocytes, but not in MA myocytes. The hypoxia-sensitive I(ss) was activated at about -50 mV; thus, some of the channels responsible for this current may be open at the resting membrane potential (-40 ± 1 mV) of PA cells used in this study. Hypoxia also significantly depolarized PA cells bathed in PSS (1.8 mM Ca2+) from -40.7 ± 1.3 to -24.0 ± 2.4 mV, and PA cells bathed in Ca2+-free PSS (0.1 mM EGTA) from -38.4 ± 1.3 to -26.1 ± 3.9 mV. The hypoxia-induced inhibition of I(out) in PA cells was accompanied by an apparent increase in inward Ca2+ current. Removal of extracellular Ca2+ and addition of 2 mM EGTA to the bath solution while maintaining a Ca2+-free intracellular solution with 10 mM EGTA in the pipette (to prevent Ca2+-activated K+ channels from opening) did not preclude the hypoxia- induced inhibition of I(out) in PA cells. These data indicate that hypoxia attenuates voltage-gated K+ channel activity in PA cells but not in MA cells. The mechanism by which hypoxia inhibits I(out) is not known, but might be related to inhibition of oxidative metabolism. This inhibition of I(out) depolarizes the PA cells. By secondarily opening voltage-gated Ca2+ channels and promoting Ca2+ entry, the block of these K+ channels might be responsible for initiating hypoxia-induced pulmonary vasoconstriction.
KW - hypoxia
KW - patch- clamp technique
KW - potassium channel
KW - pulmonary arterial smooth muscle cells
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M3 - Article
VL - 264
JO - American Journal of Physiology
JF - American Journal of Physiology
SN - 0363-6143
IS - 2 8-2
ER -