Slow diffusion of K+ in the T tubules of rat cardiomyocytes
| Autor: | Tævje A. Strømme, Ivar Sjaastad, Bjorn Amundsen, Ole M. Sejersted, Fredrik Swift |
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| Rok vydání: | 2006 |
| Předmět: |
Male
medicine.medical_specialty Patch-Clamp Techniques Physiology Diffusion Potassium chemistry.chemical_element Action Potentials Biology In Vitro Techniques Models Biological Contractility Physiology (medical) Internal medicine Extracellular medicine Animals Myocytes Cardiac Rats Wistar Ions Cell Membrane Biological Transport Myocardial Contraction Rats Electrophysiology Kinetics Endocrinology chemistry Biophysics |
| Zdroj: | Journal of applied physiology (Bethesda, Md. : 1985). 101(4) |
| ISSN: | 8750-7587 |
| Popis: | Cardiomyocyte contractility is regulated by the extracellular K+ concentration ([K+]o). Potassium dynamics in the T tubules during the excitation-contraction cycle depends on the diffusion rate of K+, but this rate is not known. Detubulation of rat cardiomyocytes was induced by osmotic shock using formamide, which separated the surface membrane from the T tubules. Changes in current and membrane potential in voltage-clamped (−80 mV) and current-clamped control and detubulated cardiomyocytes were compared during rapid switches between 5.4 and 8.1 mM [K+]o, and the results were simulated in a mathematical model. In the voltage-clamp experiments, the current changed significantly slower in control than in detubulated cardiomyocytes during the switch from 5.4 to 8.1 mM [K+]o, as indicated by the times to achieve 25, 50, 90, and 95% of the new steady-state current [control (ms) t25 = 98 ± 12, t50 = 206 ± 20, t90 = 570 ± 72, t95 = 666 ± 92; detubulated t25 = 61 ± 11, t50 = 142 ± 17, t90 = 352 ± 52, t95 = 420 ± 69]. These time points were not significantly different either during the 8.1 to 5.4 mM [K+]o switch or in current-clamped cardiomyocytes switching from 5.4 to 8.1 mM [K+]o. Mathematical simulation of the difference current between control and detubulated cardiomyocytes gave a t-tubular diffusion rate for K+ of ∼85 μm2/s. We conclude that the diffusion of K+ in the T tubules is so slow that they constitute a functional compartment. This might play a key role in local regulation of the action potential, and thus in the regulation of cardiomyocyte contractility. |
| Databáze: | OpenAIRE |
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