Cardiomyocyte t-tubular fluid pumping

Abstract

T-tubuli (TT), sarcolemmal membrane invaginations of (cardio-)myocytes that underlie excitation-contraction coupling, form an intricate network of fluid-filled conduits. Although continuous with the extracellular space, their narrow lumen and the tortuous structure can form domains of restricted diffusion. Combined with unequal ion fluxes across ’outer’ cell surface and TT membranes, this may generate ion gradients in TT that could may be incompatible with function, especially deep in the TT network and at high pacing rates.