Abstract
The time course and magnitude of the Ca(2+) fluxes underlying spontaneous Ca(2+) waves in single permeabilized ventricular cardiomyocytes were derived from confocal Fluo-5F fluorescence signals. Peak flux rates via the sarcoplasmic reticulum (SR) release channel (RyR2) and the SR Ca(2+) ATPase (SERCA) were not constant across a range of cellular [Ca(2+)] values. The Ca(2+) affinity (K(mf)) and maximum turnover rate (V(max)) of SERCA and the peak permeability of the RyR2-mediated Ca(2+) release pathway increased at higher cellular [Ca(2+)] loads. This information was used to create a computational model of the Ca(2+) wave, which predicted the time course and frequency dependence of Ca(2+) waves over a range of cellular Ca(2+) loads. Incubation of cardiomyocytes with the Ca(2+) calmodulin (CaM) kinase inhibitor autocamtide-2-related inhibitory peptide (300 nM, 30 mins) significantly reduced the frequency of the Ca(2+) waves at high Ca(2+) loads. Analysis of the Ca(2+) fluxes suggests that inhibition of CaM kinase prevented the increases in SERCA V(max) and peak RyR2 release flux observed at high cellular [Ca(2+)]. These data support the view that modification of activity of SERCA and RyR2 via a CaM kinase sensitive process occurs at higher cellular Ca(2+) loads to increase the maximum frequency of spontaneous Ca(2+) waves.
Original language | English |
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Pages (from-to) | 2581-2595 |
Number of pages | 15 |
Journal | Biophysical Journal |
Volume | 93 |
Issue number | 7 |
DOIs | |
Publication status | Published - 1 Oct 2007 |
Keywords
- Animals
- Calcium/metabolism
- Calmodulin/metabolism
- Computer Simulation
- Fluorescent Dyes/pharmacology
- Kinetics
- Models, Biological
- Muscle Cells/metabolism
- Myocardium/metabolism
- Myocytes, Cardiac/metabolism
- Rabbits
- Ryanodine Receptor Calcium Release Channel/metabolism
- Sarcoplasmic Reticulum/metabolism
- Sarcoplasmic Reticulum Calcium-Transporting ATPases/metabolism