Abstract
Recently, it has become possible to record the localized fluorescence
transient associated with the opening of a single plasma membrane
Ca$^2+$ permeable ion channel using Ca$^2+$ indicators like
fluo-3. These Single Channel Ca$^2+$ Fluorescence Transients
(SCCaFTs) share some of the characteristics of such elementary events
as Ca$^2+$ sparks and Ca$^2+$ puffs caused by Ca$^2+$
release from intracellular stores (due to the opening of ryanodine
receptors and IP(3) receptors, respectively). In contrast to intracellular
Ca$^2+$ release events, SCCaFTs can be observed while simultaneously
recording the unitary channel currents using patch-clamp techniques
to verify the channel openings. Imaging SCCaFTs provides a way to
examine localized Ca$^2+$ handling in the vicinity of a channel
with a known Ca$^2+$ influx, to obtain the Ca$^2+$ current
passing through plasma membrane cation channels in near physiological
solutions, to localize Ca$^2+$ permeable ion channels on the
plasma membrane, and to estimate the Ca$^2+$ currents underlying
those elementary events where the Ca$^2+$ currents cannot be
recorded. Here we review studies of these fluorescence transients
associated with caffeine-activated channels, L-type Ca$^2+$ channels,
and stretch-activated channels. For the L-type Ca$^2+$ channel,
SCCaFTs have been termed sparklets. In addition, we discuss how SCCaFTs
have been used to estimate Ca$^2+$ currents using the rate of
rise of the fluorescence transient as well as the signal mass associated
with the total fluorescence increase.
- 15110142
- ane,
- aniline
- animals,
- bufo
- caffeine,
- calcium
- calcium,
- cell
- channel
- channels,
- compounds,
- conductivity,
- cytosol,
- dyes,
- electric
- fluorescence,
- fluorescent
- gating,
- gov't,
- in
- ion
- marinus,
- membr,
- microscopy,
- muscle,
- myocytes,
- p.h.s.,
- patch-clamp
- research
- smooth
- support,
- techniques,
- u.s.
- vitro,
- xanthenes,
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