%0 Journal Article %1 Wang_2002_242 %A Wang, Shi-Qiang %A Song, Long-Sheng %A Xu, Le %A Meissner, Gerhard %A Lakatta, Edward G %A R�os, Eduardo %A Stern, Michael D %A Cheng, Heping %D 2002 %J Biophys. J. %K 12080095 Acid, Animals, Bilayers, Calcium Calcium, Calibration, Cells, Chains, Channel, Confocal, Cultured, Dose-Response Drug, Egtazic Electrophysiology, Factors, Lipid Markov Microscopy, Myocardium, Rats, Receptor Relationship, Release Ryanodine Signal Sprague-Dawley, Thermodynamics, Time Transduction, %N 1 %P 242--251 %T Thermodynamically irreversible gating of ryanodine receptors in situ revealed by stereotyped duration of release in Ca$^2+$ sparks. %U http://www.biophysj.org/cgi/content/full/83/1/242 %V 83 %X For a single or a group of Markov channels gating reversibly, distributions of open and closed times should be the sum of positively weighted decaying exponentials. Violation of this microscopic reversibility has been demonstrated previously on a number of occasions at the single channel level, and has been attributed to possible channel coupling to external sources of free energy. Here we show that distribution of durations of Ca$^2+$ release underlying Ca$^2+$ sparks in intact cardiac myocytes exhibits a prominent mode at approximately 8 ms. Analysis of the cycle time for repetitive sparks at hyperactive sites revealed no intervals briefer than approximately 35 ms and a mode at approximately 90 ms. These results indicate that, regardless of whether Ca$^2+$ sparks are single-channel or multi-channel in origin, they are generated by thermodynamically irreversible stochastic processes. In contrast, data from planar lipid bilayer experiments were consistent with reversible gating of RyR under asymmetric cis (4 microM) and trans Ca$^2+$ (10 mM), suggesting that the irreversibility for Ca$^2+$ spark genesis may reside at a supramolecular level. Modeling suggests that Ca$^2+$-induced Ca$^2+$ release among adjacent RyRs may couple the external energy derived from Ca$^2+$ gradients across the SR to RyR gating in situ, and drive the irreversible generation of Ca$^2+$ sparks.

@article{Wang_2002_242, abstract = {For a single or a group of Markov channels gating reversibly, distributions of open and closed times should be the sum of positively weighted decaying exponentials. Violation of this microscopic reversibility has been demonstrated previously on a number of occasions at the single channel level, and has been attributed to possible channel coupling to external sources of free energy. Here we show that distribution of durations of {C}a$^{2+}$ release underlying {C}a$^{2+}$ sparks in intact cardiac myocytes exhibits a prominent mode at approximately 8 ms. Analysis of the cycle time for repetitive sparks at hyperactive sites revealed no intervals briefer than approximately 35 ms and a mode at approximately 90 ms. These results indicate that, regardless of whether {C}a$^{2+}$ sparks are single-channel or multi-channel in origin, they are generated by thermodynamically irreversible stochastic processes. In contrast, data from planar lipid bilayer experiments were consistent with reversible gating of RyR under asymmetric cis (4 microM) and trans {C}a$^{2+}$ (10 mM), suggesting that the irreversibility for {C}a$^{2+}$ spark genesis may reside at a supramolecular level. Modeling suggests that {C}a$^{2+}$-induced {C}a$^{2+}$ release among adjacent RyRs may couple the external energy derived from {C}a$^{2+}$ gradients across the SR to RyR gating in situ, and drive the irreversible generation of {C}a$^{2+}$ sparks.}, added-at = {2009-06-03T11:20:58.000+0200}, author = {Wang, Shi-Qiang and Song, Long-Sheng and Xu, Le and Meissner, Gerhard and Lakatta, Edward G and R�os, Eduardo and Stern, Michael D and Cheng, Heping}, biburl = {https://www.bibsonomy.org/bibtex/27c6f892361b7d1fd770315f52f1bcb79/hake}, description = {The whole bibliography file I use.}, file = {Wang_2002_242.pdf:Wang_2002_242.pdf:PDF}, interhash = {1a8004311aaf3a63ba40773e8af202e8}, intrahash = {7c6f892361b7d1fd770315f52f1bcb79}, journal = {Biophys. J.}, key = 203, keywords = {12080095 Acid, Animals, Bilayers, Calcium Calcium, Calibration, Cells, Chains, Channel, Confocal, Cultured, Dose-Response Drug, Egtazic Electrophysiology, Factors, Lipid Markov Microscopy, Myocardium, Rats, Receptor Relationship, Release Ryanodine Signal Sprague-Dawley, Thermodynamics, Time Transduction,}, month = Jul, number = 1, pages = {242--251}, pmid = {12080095}, timestamp = {2009-06-03T11:21:36.000+0200}, title = {Thermodynamically irreversible gating of ryanodine receptors in situ revealed by stereotyped duration of release in {C}a$^{2+}$ sparks.}, url = {http://www.biophysj.org/cgi/content/full/83/1/242}, volume = 83, year = 2002 }