The heart pumps blood against the mechanical afterload from arterial resistance, and increased afterload may alter cardiac electrophysiology and contribute to life-threatening arrhythmias. However, the cellular and molecular mechanisms underlying mechanoelectric coupling in cardiomyocytes remain unclear. We developed an innovative patch-clamp-in-gel technology to embed cardiomyocytes in a three-dimensional (3D) viscoelastic hydrogel that imposes an afterload during regular myocyte contraction. Here, we investigated how afterload affects action potentials, ionic currents, intracellular Ca²⁺ transients, and cell contraction of adult rabbit ventricular cardiomyocytes. We found that afterload prolonged action potential duration (APD), increased transient outward K⁺ current, decreased inward rectifier K⁺ current, and increased L-type Ca²⁺ current. Increased Ca²⁺ entry caused enhanced Ca²⁺ transients and contractility. Moreover, elevated afterload led to discordant alternans in APD and Ca²⁺ transient. Ca²⁺ alternans persisted under action potential clamp, indicating that the alternans was Ca²⁺ dependent. Furthermore, all these afterload effects were significantly attenuated by inhibiting nitric oxide synthase 1 (NOS1). Taken together, our data reveal a mechano-chemo-electrotransduction (MCET) mechanism that acutely transduces afterload through NOS1–nitric oxide signaling to modulate the action potential, Ca²⁺ transient, and contractility. The MCET pathway provides a feedback loop in excitation–Ca²⁺ signaling–contraction coupling, enabling autoregulation of contractility in cardiomyocytes in response to afterload. This MCET mechanism is integral to the individual cardiomyocyte (and thus the heart) to intrinsically enhance its contractility in response to the load against which it has to do work. While this MCET is largely compensatory for physiological load changes, it may also increase susceptibility to arrhythmias under excessive pathological loading.

心脏泵血对抗来自动脉阻力的机械后负荷，而增加的后负荷可能会改变心脏电生理并导致危及生命的心律失常。然而，心肌细胞机械电耦合的细胞和分子机制仍不清楚。我们开发了一种创新的膜片钳凝胶技术，将心肌细胞嵌入三维 (3D) 粘弹性水凝胶中，在常规心肌细胞收缩期间施加后负荷。在这里，我们研究了后负荷如何影响成年兔心室心肌细胞的动作电位、离子电流、细胞内 Ca ²⁺瞬变和细胞收缩。我们发现后负荷延长动作电位持续时间（APD），增加瞬时外向 K ⁺电流，减少内向整流器 K ⁺电流，增加 L 型 Ca ²⁺电流。Ca ²⁺进入增加导致Ca ²⁺瞬变和收缩性增强。此外，升高的后负荷导致 APD 和 Ca ²⁺瞬变中不一致的交替。Ca ²⁺交替糖在动作电位钳制下持续存在，表明交替糖是Ca ²⁺依赖性的。此外，所有这些后负荷效应都通过抑制一氧化氮合酶 1 (NOS1) 显着减弱。总之，我们的数据揭示了一种机械-化学-电转导 (MCET) 机制，该机制通过 NOS1-一氧化氮信号迅速转导后负荷以调节动作电位 Ca²⁺瞬态和收缩性。MCET 通路在激发-Ca ²⁺信号-收缩耦合中提供反馈回路，使心肌细胞能够响应后负荷自动调节收缩力。这种 MCET 机制是个体心肌细胞（以及心脏）不可或缺的一部分，以从本质上增强其收缩力，以响应它必须应对的负载。虽然这种 MCET 主要是对生理负荷变化的补偿，但它也可能增加在过度病理负荷下对心律失常的易感性。