inosine-diphosphate and iberiotoxin

The effects of a newly synthesized K(+) channel opener, 1-[4-(1H-imidazol-1-yl)benzoyl]-N-methylcyclobutane-carbothioamide (MCC-134) on membrane currents and intracellular Ca(2+) mobilization were investigated in rabbit portal vein smooth muscle cells. Under voltage-clamped conditions, MCC-134 dose-dependently induced K(+)-selective currents (I(MCC); EC(50) 5.3 microM) showing little desensitization but fast deactivating properties on washout of drugs. I(MCC) was completely blocked by 10 microM glibenclamide, not affected by iberiotoxin (500 nM), charybdotoxin (200 nM) or apamin (500 nM), and inhibited by nonspecific K(+) channel blockers, tetraethylammonium (1-10 mM), 4-aminopyridine (0.1-1 mM) and Ba(2+) (0.01-0.1 mM). Intracellularly applied nucleotide diphosphates (1 mM) were effective at maintaining I(MCC) (apparent potency; ADP<==GDP falling dotsIDP

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Animals; Apamin; Calcium; Charybdotoxin; Cromakalim; Dose-Response Relationship, Drug; Electrophysiology; Female; Glyburide; Imidazoles; Inosine Diphosphate; Male; Membrane Potentials; Muscle, Smooth, Vascular; Norepinephrine; Patch-Clamp Techniques; Peptides; Portal Vein; Potassium Channels; Rabbits; Thioamides; Uridine Diphosphate; Vasodilator Agents