Ca(2+)-activated and voltage-gated K+ currents in smooth muscle cells isolated from human mesenteric arteries.

摘要: 1. Smooth muscle cells were enzymatically isolated from arteries dissected mesenteric fat removed patients undergoing routine surgery. The whole-cell patch clamp technique was used to characterize the potassium (K+) currents and passive electrical properties of these cells, using high-K(+)-containing pipette solutions with either 0.2 mM EGTA or 10 BAPTA. 2. Cell capacitance, which is proportional membrane surface area, normally distributed around a value 46 pF, independent artery size between 0.4 3.6 mm. mean potential measured under current -44.1 +/- 1.9 mV (n = 52). 3. Cells dialysed in order weakly buffer intracellular Ca2+ demonstrated noisy outward an apparent threshold near -30 mV, upon superimposed spontaneous transient (STOCs). In presence, but not absence, extracellular Ca2+, this potentiated if holding depolarized into voltage range -40 +50 mV. This potentiation had bell-shaped dependency reflected activation voltage-gated channels cells. 4. blocked by externally applied tetraethylammonium (the dissociation constant, Kd 0.85 mM), as STOCs. also reduced about 40% 8 nM charybdotoxin, transiently caffeine. characteristics therefore suggested that it carried large-conductance Ca(2+)-activated K+ channels. 5. Dialysis human arterial BATPA able completely suppress current, approximately 50% amplitude recorded at positive potentials. 6. Depolarization strongly Ca(2+)-buffered presence 30 TEA block revealed residual both sustained components. These 4-aminopyridine (4-AP) similar efficiency (Kd 1.04 1.16 +60 for respectively), ranges over they inactivated, their rates recovery inactivation, significantly different. 7. different sensitivities external Cd2+ ions. (5 mM) shifted inactivation component current. (0.2 30% without affecting amplitude.(ABSTRACT TRUNCATED AT 400 WORDS)