Identification of functional voltage-gated Na+ channels in cultured human pulmonary artery smooth muscle cells

Electrical excitability, which plays an important role in excitation - contraction coupling in the pulmonary vasculature, is regulated by transmembrane ion flux in pulmonary artery smooth muscle cells (PASMC). This study aimed to characterize the electrophysiological properties and molecular identities of voltage-gated Na+ channels in cultured human PASMC. We recorded tetrodotoxin (TTX) sensitive and rapidly inactivating Na+ currents with properties similar to those described in cardiac myocytes. Using RT-PCR, we detected transcripts of seven Na+ channel alpha genes (SCN2A, 3A, 4A, 7A, 8A, 9A, and 11A), and two beta subunit genes (SCN1B and 2B). Our results demonstrate that human PASMC express TTX-sensitive voltage-gated Na+ channels. Their physiological functions remain unresolved, although our data suggest that Na+ channel activity does not directly influence membrane potential, intracellular Ca2+ release, or proliferation in normal human PASMC. Whether their expression and/or activity are heightened in the pathological state is discussed.