Stretch-activated channels (SACs) have been found in smooth muscle
and are thought to be involved in myogenic responses. Although SACs
have been shown to be Ca$^2+$ permeable when Ca$^2+$ is the
only charge carrier, it has not been clearly demonstrated that significant
Ca$^2+$ passes through SACs in physiological solutions. By imaging
at high temporal and spatial resolution the single-channel Ca$^2+$
fluorescence transient (SCCaFT) arising from Ca$^2+$ entry through
a single SAC opening, we provide direct evidence that significant
Ca$^2+$ can indeed pass through SACs and increase the local Ca$^2+$.
Results were obtained under conditions where the only source of Ca$^2+$
was the physiological salt solution in the patch pipette containing
2 mM Ca$^2+$. Single smooth muscle cells were loaded with fluo-3
acetoxymethyl ester, and the fluorescence was recorded by using a
wide-field digital imaging microscope while SAC currents were simultaneously
recorded from cell-attached patches. Fluorescence increases at the
cell-attached patch were clearly visualized before the simultaneous
global Ca$^2+$ increase that occurred because of Ca$^2+$
influx through voltage-gated Ca$^2+$ channels when the membrane
was depolarized by inward SAC current. From measurements of total
fluorescence ("signal mass") we determined that about 18\% of the
SAC current is carried by Ca$^2+$ at membrane potentials more
negative than the resting level. This would translate into at least
a 0.35-pA unitary Ca$^2+$ current at the resting potential. Such
Ca$^2+$ currents passing through SACs are sufficient to activate
large-conductance Ca$^2+$-activated K$^+$ channels and, as
shown previously, to trigger Ca$^2+$ release from intracellular
stores.
%0 Journal Article
%1 Zou_2002_6404
%A Zou, Hui
%A Lifshitz, Lawrence M
%A Tuft, Richard A
%A Fogarty, Kevin E
%A Singer, Joshua J
%D 2002
%J Proc. Natl. Acad. Sci. U. S. A.
%K 11983921 Aniline Animals, Bufo Caffeine, Calcium Calcium, Cations, Cell Channel Channels, Compounds, Conductivity, Cytosol, Dyes, Electric Electrophysiology, Factors, Fluorescence, Fluorescent Gating, Gov't, In Ion Membr, Microscopy, Muscle, Myocytes, P.H.S., Patch-Clamp Research Smooth Smooth, Spectrometry, Support, Techniques, Time U.S. Vitro, Xanthenes, ane, marinus,
%N 9
%P 6404--6409
%R 10.1073/pnas.092654999
%T Visualization of Ca$^2+$ entry through single stretch-activated
cation channels.
%U http://dx.doi.org/10.1073/pnas.092654999
%V 99
%X Stretch-activated channels (SACs) have been found in smooth muscle
and are thought to be involved in myogenic responses. Although SACs
have been shown to be Ca$^2+$ permeable when Ca$^2+$ is the
only charge carrier, it has not been clearly demonstrated that significant
Ca$^2+$ passes through SACs in physiological solutions. By imaging
at high temporal and spatial resolution the single-channel Ca$^2+$
fluorescence transient (SCCaFT) arising from Ca$^2+$ entry through
a single SAC opening, we provide direct evidence that significant
Ca$^2+$ can indeed pass through SACs and increase the local Ca$^2+$.
Results were obtained under conditions where the only source of Ca$^2+$
was the physiological salt solution in the patch pipette containing
2 mM Ca$^2+$. Single smooth muscle cells were loaded with fluo-3
acetoxymethyl ester, and the fluorescence was recorded by using a
wide-field digital imaging microscope while SAC currents were simultaneously
recorded from cell-attached patches. Fluorescence increases at the
cell-attached patch were clearly visualized before the simultaneous
global Ca$^2+$ increase that occurred because of Ca$^2+$
influx through voltage-gated Ca$^2+$ channels when the membrane
was depolarized by inward SAC current. From measurements of total
fluorescence ("signal mass") we determined that about 18\% of the
SAC current is carried by Ca$^2+$ at membrane potentials more
negative than the resting level. This would translate into at least
a 0.35-pA unitary Ca$^2+$ current at the resting potential. Such
Ca$^2+$ currents passing through SACs are sufficient to activate
large-conductance Ca$^2+$-activated K$^+$ channels and, as
shown previously, to trigger Ca$^2+$ release from intracellular
stores.
@article{Zou_2002_6404,
abstract = {Stretch-activated channels (SACs) have been found in smooth muscle
and are thought to be involved in myogenic responses. Although SACs
have been shown to be {C}a$^{2+}$ permeable when {C}a$^{2+}$ is the
only charge carrier, it has not been clearly demonstrated that significant
{C}a$^{2+}$ passes through SACs in physiological solutions. By imaging
at high temporal and spatial resolution the single-channel {C}a$^{2+}$
fluorescence transient (SCCaFT) arising from {C}a$^{2+}$ entry through
a single SAC opening, we provide direct evidence that significant
{C}a$^{2+}$ can indeed pass through SACs and increase the local [{C}a$^{2+}$].
Results were obtained under conditions where the only source of {C}a$^{2+}$
was the physiological salt solution in the patch pipette containing
2 mM {C}a$^{2+}$. Single smooth muscle cells were loaded with fluo-3
acetoxymethyl ester, and the fluorescence was recorded by using a
wide-field digital imaging microscope while SAC currents were simultaneously
recorded from cell-attached patches. Fluorescence increases at the
cell-attached patch were clearly visualized before the simultaneous
global {C}a$^{2+}$ increase that occurred because of {C}a$^{2+}$
influx through voltage-gated {C}a$^{2+}$ channels when the membrane
was depolarized by inward SAC current. From measurements of total
fluorescence ("signal mass") we determined that about 18\% of the
SAC current is carried by {C}a$^{2+}$ at membrane potentials more
negative than the resting level. This would translate into at least
a 0.35-pA unitary {C}a$^{2+}$ current at the resting potential. Such
{C}a$^{2+}$ currents passing through SACs are sufficient to activate
large-conductance {C}a$^{2+}$-activated {K}$^{+}$ channels and, as
shown previously, to trigger {C}a$^{2+}$ release from intracellular
stores.},
added-at = {2009-06-03T11:20:58.000+0200},
author = {Zou, Hui and Lifshitz, Lawrence M and Tuft, Richard A and Fogarty, Kevin E and Singer, Joshua J},
biburl = {https://www.bibsonomy.org/bibtex/273b1d8524b8ed9e13966fd06b2c4fe3d/hake},
description = {The whole bibliography file I use.},
doi = {10.1073/pnas.092654999},
file = {Zou_2002_6404.pdf:Zou_2002_6404.pdf:PDF},
interhash = {8fae9b8ee7401de55b11e0917301341d},
intrahash = {73b1d8524b8ed9e13966fd06b2c4fe3d},
journal = {Proc. Natl. Acad. Sci. U. S. A.},
key = 262,
keywords = {11983921 Aniline Animals, Bufo Caffeine, Calcium Calcium, Cations, Cell Channel Channels, Compounds, Conductivity, Cytosol, Dyes, Electric Electrophysiology, Factors, Fluorescence, Fluorescent Gating, Gov't, In Ion Membr, Microscopy, Muscle, Myocytes, P.H.S., Patch-Clamp Research Smooth Smooth, Spectrometry, Support, Techniques, Time U.S. Vitro, Xanthenes, ane, marinus,},
month = Apr,
number = 9,
pages = {6404--6409},
pii = {99/9/6404},
pmid = {11983921},
timestamp = {2009-06-03T11:21:39.000+0200},
title = {Visualization of {C}a$^{2+}$ entry through single stretch-activated
cation channels.},
url = {http://dx.doi.org/10.1073/pnas.092654999},
volume = 99,
year = 2002
}