Study On Delayed Rectifier K～+ Current Of Rabbit Vascular Smooth Muscle Cells And Comparison With Cloned Kv1.5 Channel

Whole cell patch-clamp recording techniques were used to study the characteristics of delayed rectifier K⁺ current (1_dk) in rabbit vascular smooth muscle cells (VSMC) and compare the electrophysiological properties between the I_dk in VSMC and cloned Kv1.5 channel.When the VSMC is clamped at -40 mV, depolarizing the membrane potential at increasing steps of 10 mV could evoke a series of outward potassium currents without any deactivation. The V_1/2 of the activation curve was 27.2 mV. The currents were abolished by substituting K⁺ with Cs⁺ in pipette solution and the currents decrease obviously after adding 100 mmol/L TEA or 1 mmol/L 4AP in the perfusion solution. Therefore the currents showed delayed rectifier properties. TEA inhibited the delayed rectifier potassium current with IC₅₀ of 47.8 mmol/L. At different concentrations of extracellular Ca²⁺ (1.5, 0.5 or 0 mmol/L), the currents did not change much. While 10 mM EGTA always existed in the pipette solution. Whether the whole-cell recording was made by breaking cell membrane or perforated by nystatin, the currents showed no significant differences. It looked that the currents in VSMC were little related to calcium ion.Isoprenaline (Iso) didn't influence the I_dk current in VSMC. Phenylephrine (1-50μM) increased this outward current concentration-dependent in the presence of propranolol (1 μM). The effect of phenylephrine was abolished when tetraethylammonium coexisted or cells were pretreated with prazosin. Glibenclamide 1 μM didn't influence the effect of PE obviously either.Cromakalim, a drug that could relax blood vessels and decrease blood pressure of hyperpeisis patients, could enhance the I_dk in VSMC. Several other new compounds...