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Heterogeneity of Ca2+ gating of skeletal muscle and cardiac ryanodine receptors

Copello, J A ; Barg, Sebastian LU ; Onoue, H and Fleischer, S (1997) In Biophysical Journal 73(1). p.141-156
Abstract
The single-channel activity of rabbit skeletal muscle ryanodine receptor (skeletal RyR) and dog cardiac RyR was studied as a function of cytosolic [Ca2+]. The studies reveal that for both skeletal and cardiac RyRs, heterogeneous populations of channels exist, rather than a uniform behavior. Skeletal muscle RyRs displayed two extremes of behavior: 1) low-activity RyRs (LA skeletal RyRs, approximately 35% of the channels) had very low open probability (Po < 0.1) at all [Ca2+] and remained closed in the presence of Mg2+ (2 mM) and ATP (1 mM); 2) high-activity RyRs (HA skeletal RyRs) had much higher activity and displayed further heterogeneity in their Po values at low [Ca2+] (< 50 nM), and in their patterns of activation by [Ca2+]. Hill... (More)
The single-channel activity of rabbit skeletal muscle ryanodine receptor (skeletal RyR) and dog cardiac RyR was studied as a function of cytosolic [Ca2+]. The studies reveal that for both skeletal and cardiac RyRs, heterogeneous populations of channels exist, rather than a uniform behavior. Skeletal muscle RyRs displayed two extremes of behavior: 1) low-activity RyRs (LA skeletal RyRs, approximately 35% of the channels) had very low open probability (Po < 0.1) at all [Ca2+] and remained closed in the presence of Mg2+ (2 mM) and ATP (1 mM); 2) high-activity RyRs (HA skeletal RyRs) had much higher activity and displayed further heterogeneity in their Po values at low [Ca2+] (< 50 nM), and in their patterns of activation by [Ca2+]. Hill coefficients for activation (nHa) varied from 0.8 to 5.2. Cardiac RyRs, in comparison, behaved more homogeneously. Most cardiac RyRs were closed at 100 nM [Ca2+] and activated in a cooperative manner (nHa ranged from 1.6 to 5.0), reaching a high Po (> 0.6) in the presence and absence of Mg2+ and ATP. Heart RyRs were much less sensitive (10x) to inhibition by [Ca2+] than skeletal RyRs. The differential heterogeneity of heart versus skeletal muscle RyRs may reflect the modulation required for calcium-induced calcium release versus depolarization-induced Ca2+ release. (Less)
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author
; ; and
publishing date
type
Contribution to journal
publication status
published
subject
in
Biophysical Journal
volume
73
issue
1
pages
141 - 156
publisher
Cell Press
external identifiers
  • pmid:9199779
  • scopus:0030611430
ISSN
1542-0086
language
English
LU publication?
no
id
59828610-7613-442e-9216-8b6925230780 (old id 1111601)
alternative location
http://www.biophysj.org/cgi/reprint/73/1/141
date added to LUP
2016-04-01 12:38:24
date last changed
2022-04-21 18:11:21
@article{59828610-7613-442e-9216-8b6925230780,
  abstract     = {{The single-channel activity of rabbit skeletal muscle ryanodine receptor (skeletal RyR) and dog cardiac RyR was studied as a function of cytosolic [Ca2+]. The studies reveal that for both skeletal and cardiac RyRs, heterogeneous populations of channels exist, rather than a uniform behavior. Skeletal muscle RyRs displayed two extremes of behavior: 1) low-activity RyRs (LA skeletal RyRs, approximately 35% of the channels) had very low open probability (Po &lt; 0.1) at all [Ca2+] and remained closed in the presence of Mg2+ (2 mM) and ATP (1 mM); 2) high-activity RyRs (HA skeletal RyRs) had much higher activity and displayed further heterogeneity in their Po values at low [Ca2+] (&lt; 50 nM), and in their patterns of activation by [Ca2+]. Hill coefficients for activation (nHa) varied from 0.8 to 5.2. Cardiac RyRs, in comparison, behaved more homogeneously. Most cardiac RyRs were closed at 100 nM [Ca2+] and activated in a cooperative manner (nHa ranged from 1.6 to 5.0), reaching a high Po (&gt; 0.6) in the presence and absence of Mg2+ and ATP. Heart RyRs were much less sensitive (10x) to inhibition by [Ca2+] than skeletal RyRs. The differential heterogeneity of heart versus skeletal muscle RyRs may reflect the modulation required for calcium-induced calcium release versus depolarization-induced Ca2+ release.}},
  author       = {{Copello, J A and Barg, Sebastian and Onoue, H and Fleischer, S}},
  issn         = {{1542-0086}},
  language     = {{eng}},
  number       = {{1}},
  pages        = {{141--156}},
  publisher    = {{Cell Press}},
  series       = {{Biophysical Journal}},
  title        = {{Heterogeneity of Ca2+ gating of skeletal muscle and cardiac ryanodine receptors}},
  url          = {{http://www.biophysj.org/cgi/reprint/73/1/141}},
  volume       = {{73}},
  year         = {{1997}},
}