%0 Journal Article %1 Sobi_2008_54 %A Sobie, Eric A %A Cannell, Mark B %A Bridge, John H B %D 2008 %J Biophys J %K Animals; Calcium Calcium, Cardiac; Cells, Channel Channels, Cultured; Exchanger, Function Gating, Heart Ion L-Type, Myocytes, Rabbits; Reticulum, Sarcoplasmic Signaling, Sodium, Sodium-Calcium Ventricles, Ventricular cytology; metabolism; physiology; %N 7 %P L54--L56 %R 10.1529/biophysj.107.127878 %T Allosteric activation of Na+-Ca2+ exchange by L-type Ca2+ current augments the trigger flux for SR Ca2+ release in ventricular myocytes. %U http://dx.doi.org/10.1529/biophysj.107.127878 %V 94 %X The possible contribution of Na(+)-Ca(2+) exchange to the triggering of Ca(2+) release from the sarcoplasmic reticulum in ventricular cells remains unresolved. To gain insight into this issue, we measured the "trigger flux" of Ca(2+) crossing the cell membrane in rabbit ventricular myocytes with Ca(2+) release disabled pharmacologically. Under conditions that promote Ca(2+) entry via Na(+)-Ca(2+) exchange, internal Na(+) (10 mM), and positive membrane potential, the Ca(2+) trigger flux (measured using a fluorescent Ca(2+) indicator) was much greater than the Ca(2+) flux through the L-type Ca(2+) channel, indicating a significant contribution from Na(+)-Ca(2+) exchange to the trigger flux. The difference between total trigger flux and flux through L-type Ca(2+) channels was assessed by whole-cell patch-clamp recordings of Ca(2+) current and complementary experiments in which internal Na(+) was reduced. However, Ca(2+) entry via Na(+)-Ca(2+) exchange measured in the absence of L-type Ca(2+) current was considerably smaller than the amount inferred from the trigger flux measurements. From these results, we surmise that openings of L-type Ca(2+) channels increase Ca(2+) near Na(+)-Ca(2+) exchanger molecules and activate this protein. These results help to resolve seemingly contradictory results obtained previously and have implications for our understanding of the triggering of Ca(2+) release in heart cells under various conditions.

@article{Sobi_2008_54, abstract = {The possible contribution of Na(+)-Ca(2+) exchange to the triggering of Ca(2+) release from the sarcoplasmic reticulum in ventricular cells remains unresolved. To gain insight into this issue, we measured the "trigger flux" of Ca(2+) crossing the cell membrane in rabbit ventricular myocytes with Ca(2+) release disabled pharmacologically. Under conditions that promote Ca(2+) entry via Na(+)-Ca(2+) exchange, internal [Na(+)] (10 mM), and positive membrane potential, the Ca(2+) trigger flux (measured using a fluorescent Ca(2+) indicator) was much greater than the Ca(2+) flux through the L-type Ca(2+) channel, indicating a significant contribution from Na(+)-Ca(2+) exchange to the trigger flux. The difference between total trigger flux and flux through L-type Ca(2+) channels was assessed by whole-cell patch-clamp recordings of Ca(2+) current and complementary experiments in which internal [Na(+)] was reduced. However, Ca(2+) entry via Na(+)-Ca(2+) exchange measured in the absence of L-type Ca(2+) current was considerably smaller than the amount inferred from the trigger flux measurements. From these results, we surmise that openings of L-type Ca(2+) channels increase [Ca(2+)] near Na(+)-Ca(2+) exchanger molecules and activate this protein. These results help to resolve seemingly contradictory results obtained previously and have implications for our understanding of the triggering of Ca(2+) release in heart cells under various conditions.}, added-at = {2009-06-03T11:20:58.000+0200}, author = {Sobie, Eric A and Cannell, Mark B and Bridge, John H B}, biburl = {https://www.bibsonomy.org/bibtex/24ad4395263e334357a09a144d38c5060/hake}, description = {The whole bibliography file I use.}, doi = {10.1529/biophysj.107.127878}, file = {Sobi_2008_54.pdf:Sobi_2008_54.pdf:PDF}, interhash = {d8b6113f1f290901136e9a967ed1a264}, intrahash = {4ad4395263e334357a09a144d38c5060}, journal = {Biophys J}, keywords = {Animals; Calcium Calcium, Cardiac; Cells, Channel Channels, Cultured; Exchanger, Function Gating, Heart Ion L-Type, Myocytes, Rabbits; Reticulum, Sarcoplasmic Signaling, Sodium, Sodium-Calcium Ventricles, Ventricular cytology; metabolism; physiology;}, month = Apr, number = 7, pages = {L54--L56}, pdf = {Sobi_2008_54.pdf}, pii = {S0006-3495(08)70499-5}, pmid = {18223001}, timestamp = {2009-06-03T11:21:31.000+0200}, title = {Allosteric activation of Na+-Ca2+ exchange by L-type Ca2+ current augments the trigger flux for SR Ca2+ release in ventricular myocytes.}, url = {http://dx.doi.org/10.1529/biophysj.107.127878}, volume = 94, year = 2008 }