Molecular and electrophysiological differences in the L-type Ca2+ channel of the atrium and ventricle of rat hearts.
BACKGROUND
Many pathological conditions induce electrical remodeling, possibly through intracellular Ca2+ overload, but the currently available L-type Ca2+ channel blockers may be detrimental because of their global negative inotropic effects.


RESULTS
To determine whether the L-type Ca2+ channel is identical throughout the heart, the distribution of the mRNAs and proteins comprising the L-type Ca2+ channel and its electrophysiological properties were analyzed in rat atria and ventricles. The mRNA of alpha2delta-2 (Cacna2d2) was more abundantly expressed in the atrium (approximately 5-fold) than in the ventricle. In contrast, alpha1C (Cacna1c) (Cav1.2) mRNA was significantly less abundant in the atrium. The level of the alpha1C (Cacna1c) (Cav1.2) protein was decreased (approximately 0.5-fold) and that of alpha2 delta-1 (Cacna2d1) was increased (approximately 2-fold) in the atrium compared with the ventricle. Although the peak ICa,L density showed no significant differences, voltage dependence of inactivation and activation of the current showed a more depolarized shift in the atrium than in the ventricle.


CONCLUSIONS
These results indicate that in the rat heart the L-type Ca2+ channel differs between the atrium and ventricle with regard to gene expression and electrophysiological properties.
Hatano
Seiji
S
The Cardiovascular Institute, Tokyo, Japan. shatano-circ@umin.ac.jp
Yamashita
Takeshi
T
Sekiguchi
Akiko
A
Iwasaki
Yuki
Y
Nakazawa
Kiyoshi
K
Sagara
Koichi
K
Iinuma
Hiroyuki
H
Aizawa
Tadanori
T
Fu
Long-Tai
LT
D000818:Animals; D016275:Atrial Function; D015220:Calcium Channels / Q000032:analysis / Q000235:genetics; D020746:Calcium Channels, L-Type / Q000032:analysis* / Q000235:genetics; D004594:Electrophysiology; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology; D006325:Heart Atria / Q000737:chemistry*; D006352:Heart Ventricles / Q000737:chemistry*; D018408:Patch-Clamp Techniques; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D016276:Ventricular Function
C504728:Cacna1c protein, rat; C486060:Cacna2d1 protein, rat; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D012333:RNA, Messenger