期刊
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
卷 334, 期 4, 页码 1135-1140出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.bbrc.2005.06.203
关键词
excitation-contraction coupling; tetrodotoxin sensitivity/resistance; T-tubules; plasmalemma; cell imaging; scanning probe microscopy; near-field microscopy; membrane protein localization; ion channels
Cardiac voltage-dependent sodium channels (VDSC) are known to be tetrodotoxin (TTX)-resistant. However, recent immunochemical studies suggest the presence of TTX-sensitive neuronal-type VDSC in the heart. Scanning ion conductance microscopy (SICM) coupled to electrophysiology was used to obtain more direct functional evidence. TTX sensitivities of whole-cell sodium currents (I-Na) in control and detubulated cells were compared. Addition of 200 nM TTX decreased I-Na. of control cells by 20%, whereas detubulated cells were hardly effected. The remaining current peaked slightly earlier and inactivation decay was faster (as in neuronal VDSC) than in detubulated cells. Single-channel activity was first assayed at random on the plasmalemma, and after topography had been revealed by SICM, at patched T-tubules openings. In the latter case, a single-channel conductance of 11-12 pS was observed with a higher rate of success. This study provides independent evidence for neuronal VDSC in cardiomyocytes where they could rapidly and synchronously couple T-tubule and cell surface depolarizations. (c) 2005 Elsevier Inc. All rights reserved.
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