[Transmural heterogeneity of calcium handling proteins in the mechanism of porcine model of ventricular fibrillation].
OBJECTIVE
To investigate the role of heterogeneous expression of calcium handling proteins and spatial heterogeneity of APD restitution in the maintenance mechanism of ventricular fibrillation.


METHODS
During programmed electrical simulation, APD restitution curves in the endocardium and epicardium of LV were constructed by plotting APD100 and diastolic interval. APD alternans, delayed after depolarization events were recorded simultaneously. Endocardial and epicardial myocytes were isolated from LV base and apex. Real time-PCR and Western blotting were performed to determine the relative messenger RNA and protein expression levels of calcium handling proteins.


RESULTS
The normal hearts have spatial heterogeneity of action potential restitution property and transmural heterogeneity of calcium handling proteins. The slopes of the APD restitution curve in the endocardium were significantly steeper than those in epicardium, and the slopes of APD curve at the LV apex were significantly steeper than those in LV base. However, delayed after depolarization events with larger amplitude and earlier onset consistently occurred in the endocardium of LV base. After programmed electrical simulation, the expression of messenger RNA of RyR2, SERCA2a except for Calstabin2 significantly decreased (by 57% and 41%, respectively, P < 0.05) in the endocardium of the base, while the expression of RyR2, SERCA2a, Calstabin2 significantly increased (by 90%, 78%and 64%, respectively, P < 0.05) in the epicardium of LV base. Although transmural heterogeneity of calcium handling proteins at the LV apex were also observed after rapid pacing, there is no significant differences in the transmural heterogeneity at the LV apex compared to the LV base. The base of LV has unique calcium handling properties.


CONCLUSIONS
It has been shown that Calcium cycling could modulate APD restitution property in the intact heart. The interaction between action potential and calcium dynamics instabilities is one of the most important reasons why simple criterion such as the APD restitution slope > 1 may fail to accurately predict the onset of APD alternans.
Lü
Jing-jun
JJ
Department of Emergency Medicine, Renmin Hospital of Wuhan University, Wuhan 430060, China.
Lin
Guo-sheng
GS
Zhao
Dong-dong
DD
Cui
Bo
B
Wei
Jie
J
Bao
Ming-wei
MW
D000200:Action Potentials; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism*; D008297:Male; D013552:Swine; D014693:Ventricular Fibrillation / Q000378:metabolism* / Q000503:physiopathology*
D002147:Calmodulin; D002118:Calcium