Note: the following is a local copy of a page from the Rudy lab web site: http://rudylab.wustl.edu/research/cell/methodology/cellmodels/HRd/HRD%20on%20the%20web/HRD%20Introduction.html .

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The Hund-Rudy Dynamic (HRd) Model of the Canine Ventricular Myocyte

The Hund-Rudy dynamic (HRd) model is based on data from the canine epicardial ventricular myocyte. Rate-dependent phenomena associated with ion channel kinetics, action potential properties and Ca^2+ handling are simulated by the model. Distinguishing features of the HRd include (1) regulation of Ca^2+-handling by Ca^2+/calmodulin dependent protein kinase (CaMKII), (2) incorporation of the late Na^+ current (INaL) and Ca^2+ dependent transient outward current (Ito2, in addition to Ito1), (3) dynamic intracellular Cl^- handling and (4) a novel formulation of calcium release from the junctional sarcoplasmic reticulum (JSR). Interaction between dihydropyridine receptors (ICaL) and ryanodine receptors (RyR) occurs in a restricted Ca^2+ subspace. The calcium release formulation incorporates activation of RyR by ICaL, Ca^2+-dependent inactivation of RyR, and modulation of RyR open-probability by both JSR and subspace Ca^2+.

Originally published in:

                        "Rate dependence and regulation of action potential and calcium transient
                                in a canine cardiac ventricular cell model."
                                Hund TJ, Rudy Y.
Circulation. 2004 Nov 16;110(20):4008-74.

ERRATUM:

In the online supplement for the HRD code, there is a typo in the formulation of the Na⁺ current rate constant . The equation should read:

If mV,

SIMULATION NOTES :

Note on achieving steady state during ultra-long term continuous pacing.

Note on modifications to HRD code for simulation of propagation.

To directly access the C++ code, (Last updated on September 29, 2005) click here .

To download the Matlab code, (Last updated on October 5, 2005. Backward Compatibility with Matlab 6.5) click here .

For sample output, and directions on how to use the code click here.

To view a concise description of the model formulations, click here.

Question about the model? Email Tom Hund. Question about the code? Email Keith Decker

Linked Index to the C++ Code and Descriptions of Formulations

A. Currents	Variable	Formulation	Code
1. fast Na+ current	ina	link	definition	implementation
2. late Na+ current	inal	link	definition	implementation
3. L-type Ca2+ current	ical	link	definition	implementation
4. rapid delayed rectifier K+ current	ikr	link	definition	implementation
5. slow delayed rectifier K+ current	iks	link	definition	implementation
6. 4AP-sensitive transient outward K+ current	ito1	link	definition	implementation
7. Ca2+ dependent transient outward Cl- current	ito2	link	definition	implementation
8. time- independent K+ current	ik1	link	definition	implementation
9. background Ca2+ current	icab	link	definition	implementation
10. plateau K+ current	ikp	link	definition	implementation
11. Cl- background current	iclb	link	definition	implementation
B. Pumps and Exchangers
1. Na+-Ca2+ exchanger	inaca	link	definition	implementation
2. Na+-K+ pump	inak	link	definition	implementation
3. Sarcolemmal Ca2+ pump	ipca	link	definition	implementation
C. Transporters
1. Na+-Cl- cotransporter	ctnacl	link	definition	implementation
2. K+-Cl- cotransporter	ctkcl	link	definition	implementation
D. Ionic Fluxes
1. Ca2+ leak from JSR to myoplasm	qleak	link	definition	implementation
2. Ca2+ release from JSR to subspace	qrelease	link	definition	implementation
3. Ca2+ transfer from NSR to JSR	qtr	link	definition	implementation
4. Ca2+ uptake from myoplasm to NSR	qup	link	definition	implementation
E. Dynamic Concentrations
1. myoplasmic Na+	nai	link		implementation
2. myoplasmic K+	ki	link		implementation
3. myoplasmic Cl-	cli	link		implementation
4. myoplasmic Ca2+	cai	link		implementation
5. JSR Ca2+	cajsr	link		implementation
6. NSR Ca2+	cansr	link		implementation
7. restricted space Ca2+	car	link		implementation
8. CaMKinase	camk	link		implementation