%0 Journal Article %1 Thom_2003_1325 %A Thomas, Marion J %A Sjaastad, Ivar %A Andersen, Kathrine %A Helm, P. Johannes %A Wasserstrom, J. Andrew %A Sejersted, Ole M %A Ottersen, Ole Petter %D 2003 %J J. Mol. Cell. Cardiol. %K 14596788 Animals, Antibodies, Antibody Blotting, Calcium Calcium, Cardiac, Cells, Channel, Channels, Comparative Confocal, Cultured, Direct, Exchanger, Fluorescent Formamides, Gov't, Heart Immunoelectron, Immunohistochemistry, L-Type, Membrane Microscopy, Microtubules, Monoclonal, Myocardium, Myocytes, Non-U.S. P.H.S., Patch-Clamp Potentials, Rabbits, Rats, Receptor Release Research Ryanodine Sarcolemma, Sodium, Sodium-Calcium Study, Support, Technique, Techniques, U.S. Ventricles, Western, %N 11 %P 1325-37 %T Localization and function of the Na$^+$/Ca$^2+$-exchanger in normal and detubulated rat cardiomyocytes. %U http://dx.doi.org/10.1016/j.yjmcc.2003.08.005 %V 35 %X It is controversial whether the Na$^+$/Ca$^2+$-exchanger (NCX) can induce cardiomyocyte contraction through reverse-mode exchange and Ca$^2+$-induced Ca$^2+$ release (CICR). Information about the spatial distribution and functional activity within different sarcolemmal (SL) regions could shed light on this potential role. We raised a new antibody to the NCX and showed by confocal laser scanning microscopy (CLSM) that immunoreactivity is strongly expressed throughout the surface SL and intercalated disk regions with punctate labeling of the vertical transverse (T)-tubules but not the longitudinal T-tubules. Immuno-electron microscopy confirmed CLSM observations. Gold particles associated with the exchanger were within nanometer range of particles signaling ryanodine receptors. A similar close association was found between the L-type Ca$^2+$ channel (known to be concentrated in the dyad) and ryanodine receptors. In whole-cell patch-clamped cardiomyocytes, peak I(NCX) (measured at 90 mV) decreased by approximately 40\% (497 +/- 32 vs. 304 +/- 12 pA, P < 0.001) after detubulation, while membrane capacitance decreased by 27\% (204 +/- 11 vs. 150 +/- 7 pF, P < 0.01) thus giving a small but significant 16\% reduction in current density. Thus, the density and/or functional activity of the NCX is greater in the vertical T-tubules than in the longitudinal T-tubules, surface SL or disk regions, pointing to important functional differences between these plasma membrane domains. Our combined co-immunolocalization and physiological data suggest that the NCX has multiple functions depending upon membrane location. We suggest the possibility that NCX modulates CICR, sarcoplasmic reticulum Ca$^2+$ load, and that it also serves to regulate Ca$^2+$ handling in neighboring cells.

@article{Thom_2003_1325, abstract = {It is controversial whether the {N}a$^{+}$/{C}a$^{2+}$-exchanger (NCX) can induce cardiomyocyte contraction through reverse-mode exchange and {C}a$^{2+}$-induced {C}a$^{2+}$ release (CICR). Information about the spatial distribution and functional activity within different sarcolemmal ({SL}) regions could shed light on this potential role. We raised a new antibody to the NCX and showed by confocal laser scanning microscopy ({CLSM}) that immunoreactivity is strongly expressed throughout the surface {SL} and intercalated disk regions with punctate labeling of the vertical transverse (T)-tubules but not the longitudinal T-tubules. Immuno-electron microscopy confirmed {CLSM} observations. Gold particles associated with the exchanger were within nanometer range of particles signaling ryanodine receptors. A similar close association was found between the L-type {C}a$^{2+}$ channel (known to be concentrated in the dyad) and ryanodine receptors. In whole-cell patch-clamped cardiomyocytes, peak I(NCX) (measured at 90 mV) decreased by approximately 40\% (497 +/- 32 vs. 304 +/- 12 pA, P < 0.001) after detubulation, while membrane capacitance decreased by 27\% (204 +/- 11 vs. 150 +/- 7 pF, P < 0.01) thus giving a small but significant 16\% reduction in current density. Thus, the density and/or functional activity of the NCX is greater in the vertical T-tubules than in the longitudinal T-tubules, surface {SL} or disk regions, pointing to important functional differences between these plasma membrane domains. Our combined co-immunolocalization and physiological data suggest that the NCX has multiple functions depending upon membrane location. We suggest the possibility that NCX modulates CICR, sarcoplasmic reticulum {C}a$^{2+}$ load, and that it also serves to regulate {C}a$^{2+}$ handling in neighboring cells.}, added-at = {2009-06-03T11:20:58.000+0200}, author = {Thomas, Marion J and Sjaastad, Ivar and Andersen, Kathrine and Helm, P. Johannes and Wasserstrom, J. Andrew and Sejersted, Ole M and Ottersen, Ole Petter}, biburl = {https://www.bibsonomy.org/bibtex/2a89b660ca29dd1385f71f3c65c25133b/hake}, description = {The whole bibliography file I use.}, file = {Thom_2003_1325.pdf:Thom_2003_1325.pdf:PDF}, interhash = {ec74e59bdffbc0fe54462ce2b06a8f98}, intrahash = {a89b660ca29dd1385f71f3c65c25133b}, journal = {J. Mol. Cell. Cardiol.}, key = 18, keywords = {14596788 Animals, Antibodies, Antibody Blotting, Calcium Calcium, Cardiac, Cells, Channel, Channels, Comparative Confocal, Cultured, Direct, Exchanger, Fluorescent Formamides, Gov't, Heart Immunoelectron, Immunohistochemistry, L-Type, Membrane Microscopy, Microtubules, Monoclonal, Myocardium, Myocytes, Non-U.S. P.H.S., Patch-Clamp Potentials, Rabbits, Rats, Receptor Release Research Ryanodine Sarcolemma, Sodium, Sodium-Calcium Study, Support, Technique, Techniques, U.S. Ventricles, Western,}, month = Nov, number = 11, pages = {1325-37}, pii = {S0022282803002700}, timestamp = {2009-06-03T11:21:34.000+0200}, title = {Localization and function of the {N}a$^{+}$/{C}a$^{2+}$-exchanger in normal and detubulated rat cardiomyocytes.}, url = {http://dx.doi.org/10.1016/j.yjmcc.2003.08.005}, volume = 35, year = 2003 }