Transmural Heterogeneity Of Contraction And Calcium Transient Response To Frequency And Oxidative Stress In Mouse Left Ventricular

Objective Transmural heterogeneity of contraction and calcium transient response to frequency and oxidative stress in mouse left ventricular.Methods Endocardial (Endo) and epicardial (Epi) myocytes were isolated from C57/BL6 mice by Langendorff Perfusion. Sarcomere contraction and relaxation Ca2+ transient were recorded simultaneously using a high speed CCD video camera and a dual excitation fluorescence photomultiplier system.Results:We found that the Endo myocytes have higher baseline diastolic calcium, significantly larger calcium transient and stronger sarcomere shortening than Epi myocytes. However, both the rising and declining phases for calcium transient and sarcomere shortening were slower in Endo than in Epi myocytes. When simulation frequency was increased from 1 Hz to 3 Hz, a greater percent increase in the diastole calcium level, Ca2+transient and sarcomere shortening amplitude has been observed in the Endo myocytes. Accordingly, the frequency-dependent acceleration in the decay rate of calcium transient and sarcomere relaxation was more profound in the Endo than in Epi myocytes. Perfusion of H2O2(10(100uM, for 1 min)significantly increased the amplitudes of sarcomere shortening and calcium transient in both Endo and Epi myocytes, with much greater increase in the Endo myocytes. H2O2 induced greater increase in sarcomere shortening in Endo than in Epi. Similarly, H2O2 led to great increase of Ca2+transient amplitude in Endo than in Epi myocytes. Transmural Heterogeneity of Contraction and Calcium Transient in heart failure myocytes disappeared.Conclusion:Our results suggest that the contractility of ventricular myocytes is heterogeneous. Endo myocytes have greater diastolic calcium, calcium transient amplitude and scaromere contraction. Frequency increase and oxidative stress enhance calcium transient amplitude and sarcomere contraction and relaxation. The enhancement in Endo is greater than in Epi. Transmural Heterogeneity of Contraction and Calcium Transient in heart failure myocytes disappeared.