%0 Journal Article %1 Desp_2003_3388 %A Despa, S. %A Brette, F. %A Orchard, C. H. %A Bers, D. M. %D 2003 %J Biophys. J. %K 14581240 ATPase, Animals, Calcium, Capacitance, Cardiac, Cell Cells, Comparative Cultured, Distribution, Electric Gov't, Heart Membrane Myocytes, Non-U.S. P.H.S., Potentials, Rats, Research Sarcolemma, Size, Sodium, Study, Support, Tissue U.S. Ventricles, {N}a$^{+}$-{K}$^{+}$-Exchanging %N 5 %P 3388--3396 %T Na/Ca exchange and Na/K-ATPase function are equally concentrated in transverse tubules of rat ventricular myocytes. %U http://www.biophysj.org/cgi/content/full/85/5/3388 %V 85 %X Formamide-induced detubulation of rat ventricular myocytes was used to investigate the functional distribution of the Na/Ca exchanger (NCX) and Na/K-ATPase between the t-tubules and external sarcolemma. Detubulation resulted in a 32\% decrease in cell capacitance, whereas cell volume was unchanged. Thus, the surface-to-volume ratio was used to assess the success of detubulation. NCX current (I(NCX)) and Na/K pump current (I(pump)) were recorded using whole-cell patch clamp, as Cd-sensitive and K-activated currents, respectively. Both inward and outward I(NCX) density was significantly reduced by approximately 40\% in detubulated cells. I(NCX) density at 0 mV decreased from 0.19 +/- 0.03 to 0.10 +/- 0.03 pA/pF upon detubulation. I(pump) density was also lower in detubulated myocytes over the range of voltages (-50 to +100 mV) and internal Na (Na(i)) investigated (7-22 mM). At Na(i) = 10 mM and -20 mV, I(pump) density was reduced by 39\% in detubulated myocytes (0.28 +/- 0.02 vs. 0.17 +/- 0.03 pA/pF), but the apparent K(m) for Na(i) was unchanged (16.9 +/- 0.4 vs. 17.0 +/- 0.3 mM). These results indicate that although thet-tubules represent only approximately 32\% of the total sarcolemma, they contribute approximately 60\% to the total I(NCX) and I(pump). Thus, the functional density of NCX and Na/K pump in the t-tubules is 3-3.5-fold higher than in the external sarcolemma.

@article{Desp_2003_3388, abstract = {Formamide-induced detubulation of rat ventricular myocytes was used to investigate the functional distribution of the Na/Ca exchanger (NCX) and Na/K-ATPase between the t-tubules and external sarcolemma. Detubulation resulted in a 32\% decrease in cell capacitance, whereas cell volume was unchanged. Thus, the surface-to-volume ratio was used to assess the success of detubulation. NCX current (I(NCX)) and Na/K pump current (I(pump)) were recorded using whole-cell patch clamp, as Cd-sensitive and K-activated currents, respectively. Both inward and outward I(NCX) density was significantly reduced by approximately 40\% in detubulated cells. I(NCX) density at 0 mV decreased from 0.19 +/- 0.03 to 0.10 +/- 0.03 pA/pF upon detubulation. I(pump) density was also lower in detubulated myocytes over the range of voltages (-50 to +100 mV) and internal [Na] ([Na](i)) investigated (7-22 mM). At [Na](i) = 10 mM and -20 mV, I(pump) density was reduced by 39\% in detubulated myocytes (0.28 +/- 0.02 vs. 0.17 +/- 0.03 pA/pF), but the apparent K(m) for [Na](i) was unchanged (16.9 +/- 0.4 vs. 17.0 +/- 0.3 mM). These results indicate that although thet-tubules represent only approximately 32\% of the total sarcolemma, they contribute approximately 60\% to the total I(NCX) and I(pump). Thus, the functional density of NCX and Na/K pump in the t-tubules is 3-3.5-fold higher than in the external sarcolemma.}, added-at = {2009-06-03T11:20:58.000+0200}, author = {Despa, S. and Brette, F. and Orchard, C. H. and Bers, D. M.}, biburl = {https://www.bibsonomy.org/bibtex/28d2b96fe628475cd87bd1c92be581601/hake}, description = {The whole bibliography file I use.}, file = {Desp_2003_3388.pdf:Desp_2003_3388.pdf:PDF}, interhash = {f1fa2446328af382d6e1eee04ca85d65}, intrahash = {8d2b96fe628475cd87bd1c92be581601}, journal = {Biophys. J.}, key = 66, keywords = {14581240 ATPase, Animals, Calcium, Capacitance, Cardiac, Cell Cells, Comparative Cultured, Distribution, Electric Gov't, Heart Membrane Myocytes, Non-U.S. P.H.S., Potentials, Rats, Research Sarcolemma, Size, Sodium, Study, Support, Tissue U.S. Ventricles, {N}a$^{+}$-{K}$^{+}$-Exchanging}, month = Nov, number = 5, pages = {3388--3396}, pmid = {14581240}, timestamp = {2009-06-03T11:21:09.000+0200}, title = {Na/Ca exchange and Na/K-ATPase function are equally concentrated in transverse tubules of rat ventricular myocytes.}, url = {http://www.biophysj.org/cgi/content/full/85/5/3388}, volume = 85, year = 2003 }