Inhibition of Ca(2+) sparks by ruthenium red in permeabilized rat ventricular myocytes.
We have compared the effects of the sarcoplasmic reticulum (SR) Ca(2+) release inhibitor, ruthenium red (RR), on single ryanodine receptor (RyR) channels in lipid bilayers, and on Ca(2+) sparks in permeabilized rat ventricular myocytes. Ruthenium red at 5 microM inhibited the open probability (P(o)) of RyRs approximately 20-50-fold, without significantly affecting the conductance or mean open time of the channel. At the same concentration, RR inhibited the frequency of Ca(2+) sparks in permeabilized myocytes by approximately 10-fold, and reduced the amplitude of large amplitude events (with most probable localization on the line scan) by approximately 3-fold. According to our theoretical simulations, performed with a numerical model of Ca(2+) spark formation, this reduction in Ca(2+) spark amplitude corresponds to an approximately 4-fold decrease in Ca(2+) release flux underlying Ca(2+) sparks. Ruthenium red (5 microM) increased the SR Ca(2+) content by approximately 2-fold (from 151 to 312 micromol/l cytosol). Considering the degree of inhibition of local Ca(2+) release events, the increase in SR Ca(2+) load by RR, and the lack of effects of RR on single RyR open time and conductance, we have estimated that Ca(2+) sparks under normal conditions are generated by openings of at least 10 single RyRs.
Lukyanenko
V
V
Department of Physiology, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA.
Györke
I
I
Subramanian
S
S
Smirnov
A
A
Wiesner
T F
TF
Györke
S
S
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002463:Cell Membrane Permeability; D005260:Female; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D006352:Heart Ventricles; D007700:Kinetics; D008297:Male; D009206:Myocardium / Q000166:cytology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012430:Ruthenium Red / Q000494:pharmacology*; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects / Q000502:physiology*
D019837:Ryanodine Receptor Calcium Release Channel; D012430:Ruthenium Red; D002110:Caffeine; D002118:Calcium