Evidence for tetrodotoxin-sensitive sodium currents in primary cultured myocytes from human, pig and rabbit arteries

Primary cultured human coronary myocytes express a tetrodotoxin-sensitive sodium current (I-Na). Here, we have investigated whether I-Na is expressed in vascular smooth muscles cells (VSMCs) isolated from other large arteries, and other mammals. VSMCs were enzymatically dissociated, kept in primary culture, and macroscopic I-Na was recorded using the whole-cell patch-clamp technique. We found that I-Na is expressed in VSMCs grown from human aortic (90%; n=50) and pulmonary (44%; n=19) arteries, and in the human aortic myocyte cell line HAVSMC (94%; n=27). I-Na was also detected in pig coronary (60%; n=33), and rabbit aortic (47%; n=15), but not in rat aortic VSMCs (n=20). These different I-Na had similar voltage thresholds for activation (congruent to 50 mV), and were highly sensitive to extracellularly applied tetrodotoxin. We conclude that I-Na is expressed in VSMCs grown from various types of large arteries in humans, pig and rabbit.