Author:
Krishna Abhilash,Valderrábano Miguel,Palade Philip T,Clark John W
Abstract
Abstract
Background
Rate-dependent effects on the C
a
2+ sub-system in a rat ventricular myocyte are investigated. Here, we employ a deterministic mathematical model describing various C
a
2+ signalling pathways under voltage clamp (VC) conditions, to better understand the important role of calmodulin (CaM) in modulating the key control variables C
a
2+/calmodulin-dependent protein kinase-II (CaMKII), calcineurin (CaN), and cyclic adenosine monophosphate (cAMP) as they affect various intracellular targets. In particular, we study the frequency dependence of the peak force generated by the myofilaments, the force-frequency response (FFR).
Methods
Our cell model incorporates frequency-dependent CaM-mediated spatially heterogenous interaction of CaMKII and CaN with their principal targets (dihydropyridine (DHPR) and ryanodine (RyR) receptors and the SERCA pump). It also accounts for the rate-dependent effects of phospholamban (PLB) on the SERCA pump; the rate-dependent role of cAMP in up-regulation of the L-type C
a
2+ channel (I
C
a,L
); and the enhancement in SERCA pump activity via phosphorylation of PLB.
Results
Our model reproduces positive peak FFR observed in rat ventricular myocytes during voltage-clamp studies both in the presence/absence of cAMP mediated β-adrenergic stimulation. This study provides quantitative insight into the rate-dependence of C
a
2+-induced C
a
2+-release (CICR) by investigating the frequency-dependence of the trigger current (I
C
a,L
) and RyR-release. It also highlights the relative role of the sodium-calcium exchanger (NCX) and the SERCA pump at higher frequencies, as well as the rate-dependence of sarcoplasmic reticulum (SR) C
a
2+ content. A rigorous C
a
2+ balance imposed on our investigation of these C
a
2+ signalling pathways clarifies their individual roles. Here, we present a coupled electromechanical study emphasizing the rate-dependence of isometric force developed and also investigate the temperature-dependence of FFR.
Conclusions
Our model provides mechanistic biophysically based explanations for the rate-dependence of CICR, generating useful and testable hypotheses. Although rat ventricular myocytes exhibit a positive peak FFR in the presence/absence of beta-adrenergic stimulation, they show a characteristic increase in the positive slope in FFR due to the presence of Norepinephrine or Isoproterenol. Our study identifies cAMP-mediated stimulation, and rate-dependent CaMKII-mediated up-regulation of I
C
a,L
as the key mechanisms underlying the aforementioned positive FFR.
Publisher
Springer Science and Business Media LLC
Subject
Health Informatics,Modeling and Simulation
Cited by
9 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献