HUMAN SAPHENOUS-VEIN ENDOTHELIAL-CELLS EXPRESS A TETRODOTOXIN-RESISTANT, VOLTAGE-GATED SODIUM CURRENT

Whole-cell patch-clamp electrophysiological investigation of endotheli al cells cultured from human saphenous vein (HSVECs) has identified a voltage-gated Na+ current with a mean peak magnitude of -595 +/- 49 pA (n = 75). This current was inhibited by tetrodotoxin (TTX) in a conce ntration-dependent manner, with an IC50 value of 4.7 mu M, suggesting that it was of the TTX-resistant subtype, An antibody directed against the highly conserved intracellular linker region between domains III and IV of known Na+ channel alpha-subunits was able to retard current inactivation when applied intracellularly. This antibody identified a 245-kDa protein from membrane lysates on Western blotting and positive ly immunolabeled both cultured HSVECs and intact venous endothelium, H SVECs were also shown by reverse transcription-polymerase chain reacti on to contain transcripts of the hH1 sodium channel gene. The expressi on of Na+ channels by HSVECs was shown using electrophysiology and cel l-based enzyme-linked immunosorbent assay to be dependent on the conce ntration and source of human serum. Together, these results suggest th at TTX-resistant Na+ channels of the hill isoform are expressed in hum an saphenous vein endothelium and that the presence of these channels is controlled by a serum factor.