%0 Journal Article %1 Desp_2004_1360 %A Despa, Sanda %A Kocksk�mper, Jens %A Blatter, Lothar A %A Bers, Donald M %D 2004 %J Biophys. J. %K 15298938 ATPase, Active, After Animals, Biological Biological, Cardiac, Cells, Computer Cultured, Energy Fluorescence Fluorescence, Gov't, Heart Microscopy, Models, Multiphoton, Myocytes, Non-U.S. P.H.S., Photobleaching, Rats, Recovery Research Resonance Simulation, Sodium, Support, Transfer, Transport, U.S. Ventricles, {N}a$^{+}$-{K}$^{+}$-Exchanging %N 2 %P 1360--1368 %R 10.1529/biophysj.103.037895 %T Na/K pump-induced Na(i) gradients in rat ventricular myocytes measured with two-photon microscopy. %U http://dx.doi.org/10.1529/biophysj.103.037895 %V 87 %X Via the Na/Ca and Na/H exchange, intracellular Na concentration (Na(i)) is important in regulating cardiac Ca and contractility. Functional data suggest that Na(i) might be heterogeneous in myocytes that are not in steady state, but little direct spatial information is available. Here we used two-photon microscopy of SBFI to spatially resolve Na(i) in rat ventricular myocytes. In vivo calibration yielded an apparent K(d) of 27 +/- 2 mM Na. Similar resting Na(i) was found using two-photon or single-photon ratiometric measurements with SBFI (10.8 +/- 0.7 vs. 11.1 +/- 0.7 mM). To assess longitudinal Na(i) gradients, Na/K pumps were blocked at one end of the myocyte (locally pipette-applied K-free extracellular solution) and active in the rest of the cell. This led to a marked increase in Na(i) at sites downstream of the pipette (where Na enters the myocyte and Na/K pumps are blocked). Na(i) rise was smaller at upstream sites. This resulted in sustained Na(i) gradients (up to approximately 17 mM/120 microm cell length). This implies that Na diffusion in cardiac myocytes is slow with respect to trans-sarcolemmal Na transport rates, although the mechanisms responsible are unclear. A simple diffusion model indicated that such gradients require a Na diffusion coefficient of 10-12 microm(2)/s, significantly lower than in aqueous solutions.

@article{Desp_2004_1360, abstract = {Via the Na/Ca and Na/H exchange, intracellular Na concentration ([Na](i)) is important in regulating cardiac Ca and contractility. Functional data suggest that [Na](i) might be heterogeneous in myocytes that are not in steady state, but little direct spatial information is available. Here we used two-photon microscopy of SBFI to spatially resolve [Na](i) in rat ventricular myocytes. In vivo calibration yielded an apparent K(d) of 27 +/- 2 mM Na. Similar resting [Na](i) was found using two-photon or single-photon ratiometric measurements with SBFI (10.8 +/- 0.7 vs. 11.1 +/- 0.7 mM). To assess longitudinal [Na](i) gradients, Na/K pumps were blocked at one end of the myocyte (locally pipette-applied K-free extracellular solution) and active in the rest of the cell. This led to a marked increase in [Na](i) at sites downstream of the pipette (where Na enters the myocyte and Na/K pumps are blocked). [Na](i) rise was smaller at upstream sites. This resulted in sustained [Na](i) gradients (up to approximately 17 mM/120 microm cell length). This implies that Na diffusion in cardiac myocytes is slow with respect to trans-sarcolemmal Na transport rates, although the mechanisms responsible are unclear. A simple diffusion model indicated that such gradients require a Na diffusion coefficient of 10-12 microm(2)/s, significantly lower than in aqueous solutions.}, added-at = {2009-06-03T11:20:58.000+0200}, author = {Despa, Sanda and Kocksk�mper, Jens and Blatter, Lothar A and Bers, Donald M}, biburl = {https://www.bibsonomy.org/bibtex/2866e9f06c4931598784403280be12592/hake}, description = {The whole bibliography file I use.}, doi = {10.1529/biophysj.103.037895}, file = {Desp_2004_1360.pdf:Desp_2004_1360.pdf:PDF}, interhash = {77dc8739a76f7d5134a9f087ed81acbd}, intrahash = {866e9f06c4931598784403280be12592}, journal = {Biophys. J.}, key = 65, keywords = {15298938 ATPase, Active, After Animals, Biological Biological, Cardiac, Cells, Computer Cultured, Energy Fluorescence Fluorescence, Gov't, Heart Microscopy, Models, Multiphoton, Myocytes, Non-U.S. P.H.S., Photobleaching, Rats, Recovery Research Resonance Simulation, Sodium, Support, Transfer, Transport, U.S. Ventricles, {N}a$^{+}$-{K}$^{+}$-Exchanging}, month = Aug, number = 2, pages = {1360--1368}, pii = {87/2/1360}, pmid = {15298938}, timestamp = {2009-06-03T11:21:10.000+0200}, title = {Na/K pump-induced [Na](i) gradients in rat ventricular myocytes measured with two-photon microscopy.}, url = {http://dx.doi.org/10.1529/biophysj.103.037895}, volume = 87, year = 2004 }