Vermij, Sarah HelenaSarah HelenaVermij0000-0002-6419-6159Abriel, HuguesHuguesAbriel0000-0003-0465-5138Kucera, JanJanKucera0000-0003-0310-69622024-10-282024-10-282020-03https://boris-portal.unibe.ch/handle/20.500.12422/181127This work discusses active and passive electrical properties of transverse (T-)tubules in ventricular cardiomyocytes to understand the physiological roles of T-tubules. T-tubules are invaginations of the lateral membrane that provide a large surface for calcium-handling proteins to facilitate sarcomere shortening. Higher heart rates correlate with higher T-tubular densities in mammalian ventricular cardiomyocytes. We assess ion dynamics in T-tubules and the effects of sodium current in T-tubules on the extracellular potential, which leads to a partial reduction of the sodium current in deep segments of a T-tubule. We moreover reflect on the impact of T-tubules on macroscopic conduction velocity, integrating fundamental principles of action potential propagation and conduction. We also theoretically assess how the conduction velocity is affected by different T-tubular sodium current densities. Lastly, we critically assess literature on ion channel expression to determine whether action potentials can be initiated in T-tubules.en500 - Science::570 - Life sciences; biology600 - Technology::610 - Medicine & healtharticle10.7892/boris.1318203126941810.1016/j.bbamcr.2019.06.016