%0 Journal Article %1 Meji_1999_177 %A Mej�a-Alvarez, R. %A Kettlun, C. %A R�os, E. %A Stern, M. %A Fill, M. %D 1999 %J J. Gen. Physiol. %K 9925817 Algorithms, Animals, Barium, Calcium Cesium, Channel, Channels, Diffusion, Dogs, In Magnesium, Membrane Myocardium, Patch-Clamp Potentials, Receptor Release Reticulum, Ryanodine Sarcoplasmic Techniques, Vitro, %N 2 %P 177--186 %T Unitary Ca$^2+$ current through cardiac ryanodine receptor channels under quasi-physiological ionic conditions. %U http://www.jgp.org/cgi/content/full/113/2/177 %V 113 %X Single canine cardiac ryanodine receptor channels were incorporated into planar lipid bilayers. Single-channel currents were sampled at 1-5 kHz and filtered at 0.2-1.0 kHz. Channel incorporations were obtained in symmetrical solutions (20 mM HEPES-Tris, pH 7.4, and pCa 5). Unitary Ca$^2+$ currents were monitored when 2-30 mM Ca$^2+$ was added to the lumenal side of the channel. The relationship between the amplitude of unitary Ca$^2+$ current (at 0 mV holding potential) and lumenal Ca$^2+$ was hyperbolic and saturated at approximately 4 pA. This relationship was then defined in the presence of different symmetrical CsCH3SO3 concentrations (5, 50, and 150 mM). Under these conditions, unitary current amplitude was 1.2 +/- 0.1, 0.65 +/- 0.1, and 0.35 +/- 0.1 pA in 2 mM lumenal Ca$^2+$; and 3.3 +/- 0.4, 2.4 +/- 0. 2, and 1.63 +/- 0.2 pA in 10 mM lumenal Ca$^2+$ (n > 6). Unitary Ca$^2+$ current was also defined in the presence of symmetrical Mg2+ (1 mM) and low Cs+ (5 mM). Under these conditions, unitary Ca$^2+$ current in 2 and 10 mM lumenal Ca$^2+$ was 0.66 +/- 0.1 and 1.52 +/- 0.06 pA, respectively. In the presence of higher symmetrical Cs+ (50 mM), Mg2+ (1 mM), and lumenal Ca$^2+$ (10 mM), unitary Ca$^2+$ current exhibited an amplitude of 0.9 +/- 0.2 pA (n = 3). This result indicates that the actions of Cs+ and Mg2+ on unitary Ca$^2+$ current were additive. These data demonstrate that physiological levels of monovalent cation and Mg2+ effectively compete with Ca$^2+$ as charge carrier in cardiac ryanodine receptor channels. If lumenal free Ca$^2+$ is 2 mM, then our results indicate that unitary Ca$^2+$ current under physiological conditions should be <0.6 pA.

@article{Meji_1999_177, abstract = {Single canine cardiac ryanodine receptor channels were incorporated into planar lipid bilayers. Single-channel currents were sampled at 1-5 kHz and filtered at 0.2-1.0 kHz. Channel incorporations were obtained in symmetrical solutions (20 mM {HEPES}-Tris, pH 7.4, and pCa 5). Unitary {C}a$^{2+}$ currents were monitored when 2-30 mM {C}a$^{2+}$ was added to the lumenal side of the channel. The relationship between the amplitude of unitary {C}a$^{2+}$ current (at 0 mV holding potential) and lumenal [{C}a$^{2+}$] was hyperbolic and saturated at approximately 4 pA. This relationship was then defined in the presence of different symmetrical Cs{CH}3{SO}3 concentrations (5, 50, and 150 mM). Under these conditions, unitary current amplitude was 1.2 +/- 0.1, 0.65 +/- 0.1, and 0.35 +/- 0.1 pA in 2 mM lumenal {C}a$^{2+}$; and 3.3 +/- 0.4, 2.4 +/- 0. 2, and 1.63 +/- 0.2 pA in 10 mM lumenal {C}a$^{2+}$ (n > 6). Unitary {C}a$^{2+}$ current was also defined in the presence of symmetrical [Mg2+] (1 mM) and low [Cs+] (5 mM). Under these conditions, unitary {C}a$^{2+}$ current in 2 and 10 mM lumenal {C}a$^{2+}$ was 0.66 +/- 0.1 and 1.52 +/- 0.06 pA, respectively. In the presence of higher symmetrical [Cs+] (50 mM), Mg2+ (1 mM), and lumenal [{C}a$^{2+}$] (10 mM), unitary {C}a$^{2+}$ current exhibited an amplitude of 0.9 +/- 0.2 pA (n = 3). This result indicates that the actions of Cs+ and Mg2+ on unitary {C}a$^{2+}$ current were additive. These data demonstrate that physiological levels of monovalent cation and Mg2+ effectively compete with {C}a$^{2+}$ as charge carrier in cardiac ryanodine receptor channels. If lumenal free {C}a$^{2+}$ is 2 mM, then our results indicate that unitary {C}a$^{2+}$ current under physiological conditions should be <0.6 pA.}, added-at = {2009-06-03T11:20:58.000+0200}, author = {Mej�a-Alvarez, R. and Kettlun, C. and R�os, E. and Stern, M. and Fill, M.}, biburl = {https://www.bibsonomy.org/bibtex/287404b9dec616e67ddaac0850f62d458/hake}, description = {The whole bibliography file I use.}, file = {Meji_1999_177.pdf:Meji_1999_177.pdf:PDF}, interhash = {ca4ffbdf9dee5e78d6f74b7e6b7cbdec}, intrahash = {87404b9dec616e67ddaac0850f62d458}, journal = {J. Gen. Physiol.}, key = 250, keywords = {9925817 Algorithms, Animals, Barium, Calcium Cesium, Channel, Channels, Diffusion, Dogs, In Magnesium, Membrane Myocardium, Patch-Clamp Potentials, Receptor Release Reticulum, Ryanodine Sarcoplasmic Techniques, Vitro,}, month = Feb, number = 2, pages = {177--186}, pmid = {9925817}, timestamp = {2009-06-03T11:21:22.000+0200}, title = {Unitary {C}a$^{2+}$ current through cardiac ryanodine receptor channels under quasi-physiological ionic conditions.}, url = {http://www.jgp.org/cgi/content/full/113/2/177}, volume = 113, year = 1999 }