Key result
Three-dimensional reconstruction of the transverse-axial tubular system in guinea pig cardiomyocytes revealed it comprises 52.6% of the total plasma membrane, supporting its role in K+ accumulation.
The TATS in guinea pig cardiomyocytes forms a substantial restricted extracellular compartment that likely plays a key role in K+ accumulation-depletion phenomena at the single-cell level.
May implicate TATS in cardiomyocyte K+ accumulation; leaves open human validation and clinical relevance.
K+ accumulation-depletion (AD) phenomena were found in single guinea pig ventricular myocytes using the patch-clamp method in whole cell configuration. We suggest that the cardiomyocyte transverse-axial tubular system (TATS) lumen is the restricted extracellular space where the K+ AD could take place. A three-dimensional (3D) reconstruction of the TATS in a cardiomyocyte segment from serial ultrafine sections was made by three-dimensional isosurface rendering and quantitative data were obtained from the image processing. This original approach of the TATS intricated network gave a new vision of this membrane system; moreover, quantitative data about the tubular membrane importance (52.6% of the total plasma membrane) and its surface area versus the tubular volume fraction (STATS/VTATS = 13.5 micron 2/micron 3) would fit in the electrophysiological results. The hypothesis whereby this 'extracellular' compartment could play, in single cells, a role as important as that of narrow clefts in the whole heart is discussed.
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Amsellem et al. (1995) studied this question. 3D reconstruction of the transverse-axial tubular system was evaluated on Tubular membrane importance and surface area versus tubular volume fraction. Three-dimensional reconstruction of the transverse-axial tubular system in guinea pig cardiomyocytes revealed it comprises 52.6% of the total plasma membrane, supporting its role in K+ accumulation.
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