Upregulation of TRPC1 Contributes to Contractile Function in Isoproterenol-induced Hypertrophic Myocardium of Rat

Aims: The transient receptor potential canonical channel 1 (TRPC1) is a crucial component of the stretch-activated ion channels (SACs). The objective of this research was to demonstrate the contribution of TRPC1 in maintaining cardiac contractile function in the hypertrophic myocardium. Methods: Hypertrophic rat hearts were induced by injecting isoproterenol intraperitoneally, and the expressions of TRPC1/3/6 and Na+/Ca2+ exchanger 1 (NCX1) proteins were analyzed by Western blot. The intracellular calcium images, the action potential of myocardium, the length-dependent contractile force of ventricle muscle and the cardiac output of isolated heart were investigated. Results: The expression of TRPC1 was increased in the hypertrophic myocardium. After being stretched, the ascendant amplitude of the increase in the intracellular calcium ion concentration ([Ca2+]i) in the hypertrophic myocardium was higher than that in the normal myocardium. The increase of the APD50 and the amplitude of the membrane potential depolarization were more significant in the hypertrophic myocardium after the activation of SACs. When the heart preparations were perfused with Tyrode's solution, there was no difference in the cardiac systolic function between the cardiac hypertrophy group and the control group. Gadolinium, a SACs blocker, reduced the length-dependent contractile force and suppressed the ascending limb of the Frank-Starling curves in the hypertrophic heart. Conclusions: The upregulation of TRPC1 contributes to the contractile function in the hypertrophic myocardium by increasing [Ca2+]i through the SACs