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[The characteristics and oxidative modulation of large-conductance calciumactivated potassium channels in guinea-pig colon smooth muscle cells.] [Ariticle in Chinese]

HUANG Wei-Feng, OUYANG Shou^*, ZHANG Hui

Xiamen Medical Research Institute, Xiamen 361003, China

Abstract

To investigate the characteristics of large-conductance calcium-activated potassium channels (BKCa) and the effect of hydrogen peroxide (H2O2) on BKCa in guinea-pig proximal colon smooth muscle cells, single smooth muscle cells of guinea-pig colon were enzymatically isolated in low calcium solution containing papain (3 mg/mL), DTT (2 mg/mL), and bovine serum albumin (BSA, 2 mg/mL). Tissues were incubated at 36 ºC in enzyme solution for 15 min and were then suspended in enzyme-free low calcium solution. Inside-out single channel recording technique was used to record BKCa current. The intracellular (bath) and microelectrode solution both contained symmetrical high potassium. The BKCa in guinea-pig colon smooth muscle cell possesses: 1) voltage-dependence, 2) high selectivity for potassium ion, 3) large conductance (223.7 pS±9.2 pS), 4) dependence of [Ca2+]i. Intracellular application of H2O2 decreased the open probability (Po) of BKCa at low concentration (≤1 mmol/L), and increased or decreased Po of BKCa at high concentration (5 mmol/L), without affecting the unitary conductance. The effects of H2O2 were reversed by reducing agent dithiothreitol (DTT). Similarly, cysteine specific oxidizing agent, DTNB, also increased or decreased Po of BKCa and DTT partially reversed the effect of DTNB. It is thus suggested that H2O2 and DTNB may modulate Po of BKCa via the oxidation of cysteine residue.

Key words: Hydrogen peroxide; reactive oxygen species; colon; cysteine; large-conductance calcium-activated potassium channels

Received: 2009-03-30　　Accepted: 2009-04-22

Corresponding author: 欧阳守　　E-mail: xmmri@xmu.edu.cn

Citing This Article：

HUANG Wei-Feng, OUYANG Shou, ZHANG Hui. [The characteristics and oxidative modulation of large-conductance calciumactivated potassium channels in guinea-pig colon smooth muscle cells.] [Ariticle in Chinese] . Acta Physiol Sin 2009; 61 (3): 285-291 (in Chinese with English abstract).