Inhibition of Ca2+ Sparks by Ruthenium Red in Permeabilized Rat Ventricular Myocytes

Abstract

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.

The Transient Receptor Potential Vanilloid-1 Channel in Thermoregulation: A Thermosensor It Is Not

“…s Ahluwalia et al (2002). t Ruthenium red has been reported to interact with TRPV5 (Nilius et al, 2001), TRPV6 (Nilius et al, 2001), voltage-gated calcium channel (Cibulsky and Sather, 1999), and ryanodine receptor (Lukyanenko et al, 2000).…”

Potentiation of Ca 2+ Release by cADP-Ribose in the Heart Is Mediated by Enhanced SR Ca 2+ Uptake Into the Sarcoplasmic Reticulum

“…Ca 2ϩ sparks were quantified by using a detection computer algorithm, and their statistics were corrected for missed events and amplitude distortions introduced by instrumental noise. 16,17 Data were expressed as meansϮSE. Comparisons were performed by using the paired t-test, and significance was defined at PϽ0.05.…”

“…objective. 16 Fluo-3 was excited by light at 488 nm (25-mW argon laser, intensity attenuated to 0.3%), and the fluorescence was acquired at wavelengths of Ͼ515 nm in the line scan mode at rate of 6.0 ms per scan. Ca 2ϩ sparks were quantified by using a detection computer algorithm, and their statistics were corrected for missed events and amplitude distortions introduced by instrumental noise.…”

Inositol 1,4,5-trisphosphate receptors modulate Ca2+ sparks and Ca2+ store content in vas deferens myocytes

“…The filling state of the SR must reflect the balance between the rate of loss through leak pathways and the rate of Ca 2ϩ uptake via Ca 2ϩ -ATPase. Recent studies in cardiac myocytes have suggested that Ca 2ϩ leak is more important in setting the SR load than the thermodynamic limits of the Ca 2ϩ pump (9,(16)(17)(18). It has also been postulated that the resting SR load in smooth muscle is also limited by Ca 2ϩ leak (33).…”