Predicting Local SR Ca(2+) Dynamics During Ca(2+) Wave Propagation in Ventricular Myocytes

Biophys J. 2010 Jun 2;98(11):2515-23. doi: 10.1016/j.bpj.2010.02.038.

Abstract

Of the many ongoing controversies regarding the workings of the sarcoplasmic reticulum (SR) in cardiac myocytes, two unresolved and interconnected topics are 1), mechanisms of calcium (Ca(2+)) wave propagation, and 2), speed of Ca(2+) diffusion within the SR. Ca(2+) waves are initiated when a spontaneous local SR Ca(2+) release event triggers additional release from neighboring clusters of SR release channels (ryanodine receptors (RyRs)). A lack of consensus regarding the effective Ca(2+) diffusion constant in the SR (D(Ca,SR)) severely complicates our understanding of whether dynamic local changes in SR [Ca(2+)] can influence wave propagation. To address this problem, we have implemented a computational model of cytosolic and SR [Ca(2+)] during Ca(2+) waves. Simulations have investigated how dynamic local changes in SR [Ca(2+)] are influenced by 1), D(Ca,SR); 2), the distance between RyR clusters; 3), partial inhibition or stimulation of SR Ca(2+) pumps; 4), SR Ca(2+) pump dependence on cytosolic [Ca(2+)]; and 5), the rate of transfer between network and junctional SR. Of these factors, D(Ca,SR) is the primary determinant of how release from one RyR cluster alters SR [Ca(2+)] in nearby regions. Specifically, our results show that local increases in SR [Ca(2+)] ahead of the wave can potentially facilitate Ca(2+) wave propagation, but only if SR diffusion is relatively slow. These simulations help to delineate what changes in [Ca(2+)] are possible during SR Ca(2+)release, and they broaden our understanding of the regulatory role played by dynamic changes in [Ca(2+)](SR).

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Algorithms
  • Animals
  • Calcium / metabolism*
  • Computer Simulation*
  • Cytoplasm / metabolism
  • Cytosol / metabolism
  • Diffusion
  • Heart Ventricles / metabolism*
  • Kinetics
  • Models, Cardiovascular*
  • Myocytes, Cardiac / metabolism*
  • Ryanodine Receptor Calcium Release Channel / metabolism
  • Sarcoplasmic Reticulum / metabolism*
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases / antagonists & inhibitors
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases / metabolism

Substances

  • Ryanodine Receptor Calcium Release Channel
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases
  • Calcium