Abstract: Objective To determine the characteristics of L-type calcium current(_{ICa L}) in epicardial(Epi), midmyocardial (M), and endocardial(Endo) canine ventricular myocytes. Methods Using whole-cell patch clamp techniques to compare the electrophysiological characteristics of _{ICa L} of myocytes enzymatically dissociated from right and left canine ventricular epi, mid and endomyocardium. Results The peak density of _{ICa L}(pA/pF) was –4.896±1.907(n=31), -3.406±0.904(n=37), -2.788±0.756(n=33), respectively in right ventricular(RV) epicardial, midmyocardial, and endocardial myocytes(P<0.01). The peak density of _{ICa L}(pA/pF) was -3.824±1.201(n=18), -4.854±1.485(n=20), -2.988±1.082(n=17), respectively in left ventricular(LV) (P<0.01). In epicardial myocytes, the average peak _{ICa L} densities was significantly smaller in RV than in LV(P<0.05). In midmyocardial myocytes, the average peak _{ICa L} densities was significantly larger in RV than in LV(P<0.01). In endocardial myocytes, the average peak _{ICa L} densities wasn't significantly different(P> 0.05). Conclusion L-type calcium current on different ventricular myocytes of canine present with different characteristics.

Key words: electrical heterogeneity, L-type calcium current, whole-cell patch clamp