Different Densities of Na-Ca Exchange Current in T-Tubular and Surface Membranes and Their Impact on Cellular Activity in a Model of Rat Ventricular Cardiomyocyte

0471512 - ÚT 2018 RIV US eng J - Journal Article
Pásek, Michal - Šimurda, J. - Christé, G.
Different Densities of Na-Ca Exchange Current in T-Tubular and Surface Membranes and Their Impact on Cellular Activity in a Model of Rat Ventricular Cardiomyocyte.
BioMed Research International. Roč. 2017, č. 2017 (2017), č. článku 6343821. ISSN 2314-6133. E-ISSN 2314-6141
Institutional support: RVO:61388998
Keywords : rat ventricular cell * mathematical model * Na-Ca current * t-tubules
OECD category: Biophysics
Impact factor: 2.583, year: 2017

The ratio of densities of Na-Ca exchanger current (INaCa) in the t-tubular and surface membranes (INaCa-ratio) computed from the values of INaCa and membrane capacitances (Cm) measured in adult rat ventricular cardiomyocytes before and after detubulation ranges between 1.7 and 25 (potentially even 40). Variations of action potential waveform and of calcium turnover within this span of the INaCa-ratio were simulated employing previously developed model of rat ventricular cell incorporating separate description of ion transport systems in the t-tubular and surface membranes. The increase of INaCa-ratio from 1.7 to 25 caused a prolongation of APD (duration of action potential at 90% repolarisation) by 12, 9 and 6% and an increase of peak intracellular Ca2+ transient by 45, 19 and 6% at 0.1, 1 and 5 Hz, respectively. The prolonged APD resulted from the increase of INaCa due to the exposure of a larger fraction of Na-Ca transporters to higher Ca2+ transients under t-tubular membrane. The accompanying rise of Ca2+ transient was a consequence of a higher Ca2+ load in sarcoplasmic reticulum induced by the increased Ca2+ cycling between the surface and t-tubular membranes. However, the reason for large differences in the INaCa-ratio assessed from measurements in adult rat cardiomyocytes remains to be explained.
Permanent Link: http://hdl.handle.net/11104/0268892