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Updated: Aug 11, 2026

Focal Ca2+ Transient Detection in Smooth Muscle
Published on: June 29, 2009
Sodium current in human jejunal circular smooth muscle cells
Adrian N Holm1, Adam Rich, Steven M Miller
1Department of Physiology and Biophysics, Enteric NeuroScience Program, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55905, USA.
Human jejunal smooth muscle cells possess a tetrodotoxin-insensitive sodium channel, likely SCN5A. Further research is needed to explore its role in gut motility disorders.
Area of Science:
- Gastroenterology
- Neuroscience
- Molecular Biology
Background:
- Sodium channels regulate neuronal and muscle excitability.
- Their presence in gastrointestinal smooth muscle is not well-established.
- This study investigates sodium channels in human jejunal smooth muscle.
Purpose of the Study:
- To determine the presence and characteristics of sodium currents in human jejunal circular smooth muscle cells.
- To identify the specific sodium channel alpha subunit expressed in these cells.
Main Methods:
- Patch-clamp electrophysiology was used to record ionic currents.
- Complementary DNA (cDNA) libraries were created from dissociated cells and laser-capture microdissected smooth muscle cells.
- cDNA libraries were screened for the expression of sodium channel alpha subunit messages.
Main Results:
- A tetrodotoxin-insensitive sodium (Na+) current was detected in 80% of human jejunal smooth muscle cells.
- The Na+ current activated at -65 mV, peaked at -30 mV, and exhibited a window current between -75 and -60 mV.
- Lidocaine and QX314 blocked the Na+ current, and cDNA analysis revealed high homology to SCN5A, the cardiac sodium channel alpha subunit.
Conclusions:
- Human jejunal circular smooth muscle cells express a tetrodotoxin-insensitive Na+ channel, likely SCN5A.
- The functional role of SCN5A in human gastrointestinal motility disorders requires further investigation.
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