Nitric oxide activates an iberiotoxin-sensitive potassium channel in human saphenous vein

Synthetic iberiotoxin (IBTX), an inhibitor of large conductance calcium-activated potassium channel (BKCa), was used to study the possible involvement of a specific hyperpolarizing ion channel in nitric oxide (NO)-induced venodilation. Serotonin (0.125 microM)-induced contraction of isolated human saphenous vein was dose-dependently relaxed with 50-1550 nanoM exogenous NO. 30 min preincubation of venous preparations with 90 nanoM IBTX decreased vasorelaxation induced by NO. In conclusion, a hyperpolarizing potassium channel, BKCa, may be involved in the venodilator effect of endogenous NO.