Electrical field stimulation induces endothelium-dependent contraction of human umbilical cord vessels

Electrical field stimulation (EFS) has been used for decades in classical pharmacological preparations in order to characterize the mediators released by neural endings involved in smooth muscle contraction or relaxation. Since most of the human umbilical cord has no innervation, EFS has never been used in this preparation. This study aimed to investigate the effect of EFS on vascular responsiveness from human umbilical cord. Segments of the human umbilical cord were obtained from normotensive parturients and the human umbilical artery (HUA) and the human umbilical vein (HUV) were isolated and mounted in organ bath chambers. Electrical field stimulation-induced contractions in both HUA (2.35 +/- 1.31 mN and 3.77 +/- 2.31 mN for 8 Hz and 16 Hz respectively, n = 24) and HUV (3.81 +/- 2.54 mN and 6.26 +/- 4.51 mN for 8 Hz and 16 Hz respectively, n = 25). The addition of tetrodotoxin (1 mu M) did not alter the EFS-induced contractions in both tissues (n = 5). Pre-incubation with atropine (10 and 100 mu M), glibenclamide (10 mu M) and indomethacin (10 mu M) did not affect the EFS-induced contractions in both tissues. The contractions of both vessels were significantly reduced by pre-incubation of the tissues with phentolamine (10 and 100 mu M). The endothelium removal almost abolished the EFS-induced contractions in both vessels (n = 5). In sandwich preparation, donor tissue (with endothelium) released a factor (s) that promoted contraction of the recipient tissue (endothelium removal) in both HUA and HUV (n = 5, respectively). Our findings indicate a potential role of endothelium-derived catecholamines in modulating HUA and HUV reactivities.