Article: Na+-Ca2+ exchange current from rabbit isolated atrioventricular nodal and ventricular myocytes compared using action potential and ramp waveforms.
Acta physiologica Scandinavica
2000 Volume 168, Issue 3, Page(s) 393–401
Abstract: We measured and compared Na-Ca exchanger current (INa-Ca) from rabbit isolated ventricular and atrioventricular (AV) nodal myocytes, using action potential (AP) and ramp voltage commands. Whole cell patch-clamp recordings were made at 35-37 degrees C; ... ...
Abstract | We measured and compared Na-Ca exchanger current (INa-Ca) from rabbit isolated ventricular and atrioventricular (AV) nodal myocytes, using action potential (AP) and ramp voltage commands. Whole cell patch-clamp recordings were made at 35-37 degrees C; INa-Ca was measured as 5 mM nickel (Ni)- sensitive current with major interfering voltage and calcium-activated currents blocked. In ventricular cells a 2-s descending ramp elicited INa-Ca showing outward rectification and a reversal potential (Erev) of -13.1 +/- 1. 2 mV (n = 12; mean +/- SEM). With a ventricular AP as the voltage command, the profile of INa-Ca followed the applied waveform closely. The current-voltage relation during AP repolarization was almost linear and showed an Erev of -38.3 +/- 5.3 mV (n = 6). As INa-Ca depended on the applied voltage waveform, comparisons between the two cell types utilized the same command waveform (a series of AV nodal APs). In ventricular myocytes this elicited INa-Ca that reversed near -38 mV and was inwardly directed during the pacemaker potential. This command was also applied to AV node cells; mean INa-Ca density at all voltages encompassed by the AP (-70 to +30 mV) did not differ significantly from that in ventricular myocytes (P > 0.05, ANOVA). This finding was confirmed using brief (250 ms) voltage ramp protocols (P > 0.1 ANOVA). These data represent the first direct measurements of AV nodal INa-Ca and suggest that the exchanger may be functionally expressed to similar levels in the two cell types. They may also suggest a possible role for INa-Ca during the pacemaker potential in AV node as inward INa-Ca was observed over the pacemaker potential range even with bulk internal Ca buffered to a low level. |
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MeSH term(s) | Action Potentials ; Animals ; Atrioventricular Node/metabolism ; Calcium/metabolism ; Electrophysiology ; Heart Ventricles/metabolism ; In Vitro Techniques ; Ion Transport ; Male ; Myocardium/metabolism ; Rabbits ; Sodium/metabolism ; Sodium-Calcium Exchanger/metabolism |
Chemical Substances | Sodium-Calcium Exchanger ; Sodium (9NEZ333N27) ; Calcium (SY7Q814VUP) |
Language | English |
Publishing date | 2000-03 |
Publishing country | England |
Document type | Comparative Study ; Journal Article ; Research Support, Non-U.S. Gov't |
ZDB-ID | 101-6 |
ISSN | 0001-6772 |
ISSN | 0001-6772 |
DOI | 10.1046/j.1365-201x.2000.00681.x |
Database | MEDical Literature Analysis and Retrieval System OnLINE |
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