%0 Journal Article %1 Lope_1994_21 %A L�pez-L�pez, J. R. %A Shacklock, P. S. %A Balke, C. W. %A Wier, W. G. %D 1994 %J J. Physiol. %K 7853223 Aniline Animals, Calcium Calcium, Channels, Compounds, Confocal, Dyes, Fluorescent Gov't, Heart, In Membrane Microscopy, Myocardium, Non-U.S. P.H.S., Patch-Clamp Potentials, Rats, Research Reticulum, Ryanodine, Sarcopla, Support, Techniques, U.S. Vitro, Wistar, Xanthenes, smic %P 21--29 %T Local, stochastic release of Ca$^2+$ in voltage-clamped rat heart cells: visualization with confocal microscopy. %V 480 ( Pt 1) %X 1. Confocal microscopy and the fluorescent Ca$^2+$ indicator fluo-3 (K$^+$ salt) were used to measure cytosolic free calcium ion concentration (Ca$^2+$) during excitation-contraction (E-C) coupling in single, voltage-clamped, rat cardiac ventricular cells. 2. Local Ca$^2+$i transients were measured nearly simultaneously in different, separate, subcellular volumes of approximately 2.0 microns 3. During depolarization, local Ca$^2+$i transients were distinctly different from each other and from whole-cell Ca$^2+$i transients. These differences were particularly apparent during small depolarizations, and were substantially reduced by ryanodine. 3. Components of the local Ca$^2+$i transients, particularly those evoked by small depolarizations, were closely similar, in time course and amplitude, to spontaneous local Ca$^2+$i transients, or 'sparks' (which have been shown previously to be Ca$^2+$ released from sarcoplasmic reticulum). 4. Analysis of local Ca$^2+$i transients in the spatial frequency domain (power spectrum) revealed that high power at spatial frequencies of 0.05-0.2 microns-1 was always associated with spontaneous calcium 'sparks' and with local Ca$^2+$i transients evoked by small depolarizing pulses (e.g. to -31 mV). Evoked local Ca$^2+$o transients in the presence of ryanodine, and those evoked by depolarization to very positive clamp-pulse potentials (+45 mV), were associated with considerably lower power at this frequency. 5. The results suggest that whole-cell Ca$^2+$i transients evoked by voltage-clamp depolarization, and thus by L-type Ca$^2+$ current, are comprised of local Ca$^2+$i transients that are similar to the spontaneous calcium 'sparks'. At very positive clamp-pulse potentials, however, the electrically evoked local Ca$^2+$i transients may be smaller, perhaps as a result of smaller unitary L-type Ca$^2+$ current.

@article{Lope_1994_21, abstract = {1. Confocal microscopy and the fluorescent {C}a$^{2+}$ indicator fluo-3 ({K}$^{+}$ salt) were used to measure cytosolic free calcium ion concentration ([{C}a$^{2+}$]) during excitation-contraction (E-C) coupling in single, voltage-clamped, rat cardiac ventricular cells. 2. Local [{C}a$^{2+}$]i transients were measured nearly simultaneously in different, separate, subcellular volumes of approximately 2.0 microns 3. During depolarization, local [{C}a$^{2+}$]i transients were distinctly different from each other and from whole-cell [{C}a$^{2+}$]i transients. These differences were particularly apparent during small depolarizations, and were substantially reduced by ryanodine. 3. Components of the local [{C}a$^{2+}$]i transients, particularly those evoked by small depolarizations, were closely similar, in time course and amplitude, to spontaneous local [{C}a$^{2+}$]i transients, or 'sparks' (which have been shown previously to be {C}a$^{2+}$ released from sarcoplasmic reticulum). 4. Analysis of local [{C}a$^{2+}$]i transients in the spatial frequency domain (power spectrum) revealed that high power at spatial frequencies of 0.05-0.2 microns-1 was always associated with spontaneous calcium 'sparks' and with local [{C}a$^{2+}$]i transients evoked by small depolarizing pulses (e.g. to -31 mV). Evoked local [{C}a$^{2+}$]o transients in the presence of ryanodine, and those evoked by depolarization to very positive clamp-pulse potentials (+45 mV), were associated with considerably lower power at this frequency. 5. The results suggest that whole-cell [{C}a$^{2+}$]i transients evoked by voltage-clamp depolarization, and thus by L-type {C}a$^{2+}$ current, are comprised of local [{C}a$^{2+}$]i transients that are similar to the spontaneous calcium 'sparks'. At very positive clamp-pulse potentials, however, the electrically evoked local [{C}a$^{2+}$]i transients may be smaller, perhaps as a result of smaller unitary L-type {C}a$^{2+}$ current.}, added-at = {2009-06-03T11:20:58.000+0200}, author = {L�pez-L�pez, J. R. and Shacklock, P. S. and Balke, C. W. and Wier, W. G.}, biburl = {https://www.bibsonomy.org/bibtex/291c9b49594c8dd3347ba302c87ea15be/hake}, description = {The whole bibliography file I use.}, interhash = {b5a78a9e7090a085b0e0904383933ea9}, intrahash = {91c9b49594c8dd3347ba302c87ea15be}, journal = {J. Physiol.}, keywords = {7853223 Aniline Animals, Calcium Calcium, Channels, Compounds, Confocal, Dyes, Fluorescent Gov't, Heart, In Membrane Microscopy, Myocardium, Non-U.S. P.H.S., Patch-Clamp Potentials, Rats, Research Reticulum, Ryanodine, Sarcopla, Support, Techniques, U.S. Vitro, Wistar, Xanthenes, smic}, month = Oct, pages = {21--29}, pmid = {7853223}, timestamp = {2009-06-03T11:21:21.000+0200}, title = {Local, stochastic release of {C}a$^{2+}$ in voltage-clamped rat heart cells: visualization with confocal microscopy.}, volume = {480 ( Pt 1)}, year = 1994 }