Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10769015 | Biochemical and Biophysical Research Communications | 2005 | 6 Pages |
Abstract
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 (INa) in control and detubulated cells were compared. Addition of 200Â nM TTX decreased INa 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 11-12Â 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.
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Authors
Hervé Duclohier,