Ruthenium Red Modifies the Cardiac and Skeletal Muscle Ca2+ Release Channels (Ryanodine Receptors) by Multiple Mechanisms*
- From the Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599-7260
Abstract
The effects of ruthenium red (RR) on the skeletal and cardiac muscle ryanodine receptors (RyRs) were studied in vesicle-Ca2+ flux, [3H]ryanodine binding, and single channel measurements. In vesicle-Ca2+flux measurements, RR was more effective in inhibiting RyRs at 0.2 μm than 20 μm free Ca2+. [3H]Ryanodine binding measurements suggested noncompetitive interactions between RR inhibition and Ca2+regulatory sites of RyRs. In symmetric 0.25 m KCl with 10–20 μm cytosolic Ca2+, cytosolic RR decreased single channel activities at positive and negative holding potentials. In close to fully activated skeletal (20 μmCa2+ + 2 mm ATP) and cardiac (200 μm Ca2+) RyRs, cytosolic RR induced a predominant subconductance at a positive but not negative holding potential. Lumenal RR induced a major subconductance in cardiac RyR at negative but not positive holding potentials and several subconductances in skeletal RyR. The RR-related subconductances of cardiac RyR showed a nonlinear voltage dependence, and more than one RR molecule appeared to be involved in their formation. Cytosolic and lumenal RR also induced subconductances in Ca2+-conducting skeletal and cardiac RyRs recorded at 0 mV holding potential. These results suggest that RR inhibits RyRs and induces subconductances by binding to cytosolic and lumenal sites of skeletal and cardiac RyRs.
Footnotes
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↵* This work was supported by National Institutes of Health Grants AR18687 and HL27430.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵‡ To whom correspondence should be addressed. Tel.: 919-966-5021; Fax: 919-966-2852; E-mail: meissner@med.unc.edu.
- Abbreviations:
- SR
-
sarcoplasmic reticulum
- RyR
-
ryanodine receptor
- RyR1
-
skeletal muscle RyR
- RyR2
-
cardiac muscle RyR
- RR
-
ruthenium red
- Po
-
channel open probability in the absence of a substate
- Pfull
-
open probability of full conductance events in the presence of a substate
- Psub
-
open probability of RR-related subconductances
- Ptot
-
sum of Pfull and Psub
- AMPPCP
-
adenosine 5′-(β,γ-methylenetriphosphate)
- CHAPS
-
3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate
-
- Received May 20, 1999.
- Revision received August 18, 1999.
- The American Society for Biochemistry and Molecular Biology, Inc.
