Peroxynitrite reversibly inhibits Ca2+-activated K+ channels in rat cerebral artery smooth muscle cells
Peroxynitrite reversibly inhibits Ca2+-activated K+ channels in rat cerebral artery smooth muscle cells
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DOI：
10.1152/ajpheart.2000.278.6.h1883
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发表时间：
2000-06-01
影响因子：
4.8
通讯作者：
Elliott, SJ
中科院分区：
文献类型：
--
作者：
Brzezinska, AK;Gebremedhin, D;Elliott, SJ
过氧亚硝酸盐(ONOO-)是一种大鼠大脑中动脉收缩激动剂。为了确定ONOO生物活性的这一部分的机制，本研究观察了ONOO-对大鼠脑动脉离子电流和通道活性的影响。电压钳制细胞的全细胞记录是在优化K+电流的条件下设计的。测定大电导钙激活钾(BK)通道的选择性阻断剂Iberiooxin和ONOO-(10-100mU/M)的作用。在吸管电位为150 mV时，ONOO抑制了39%的IBS敏感电流。ONOO-对毒副作用敏感电流具有选择性，而分解后的ONOO-对电流无影响。在切除的、由内向外的膜片中，使用对称的K+溶液记录通道活动。单位电流对细胞内钙离子浓度升高敏感，与BK通道的活动一致。内源性ONOO通过减少开放概率和平均开放时间而剂量依赖性地抑制通道活动。ONOO-的抑制作用可被还原型谷胱甘肽所克服。在ONOO-之后加入谷胱甘肽，将整个细胞的电流幅度恢复到控制水平，并恢复单通道门控以控制行为。ONOO-对离体脑动脉和单个心肌细胞膜K+电流的抑制作用与其收缩作用一致。综上所述，我们的数据表明，ONOO-有可能通过抑制BK通道活动来改变脑血管张力。
Peroxynitrite (ONOO-) is a contractile agonist of rat middle cerebral arteries. To determine the mechanism responsible for this component of ONOO- bioactivity, the present study examined the effect of ONOO- on ionic current and channel activity in rat cerebral arteries. Whole cell recordings of voltage-clamped cells were made under conditions designed to optimize K+ current. The effects of iberiotoxin, a selective inhibitor of large-conductance Ca2+-activated K+ (BK) channels, and ONOO- (10-100 mu M) were determined. At a pipette potential of 150 mV, ONOO- inhibited 39% of iberiotoxin-sensitive current. ONOO- was selective for iberiotoxin-sensitive current, whereas decomposed ONOO- had no effect. In excised, inside-out membrane patches, channel activity was recorded using symmetrical K+ solutions. Unitary currents were sensitive to increases in internal Ca2+ concentration, consistent with activity due to BK channels. Internal ONOO- dose dependently inhibited channel activity by decreasing open probability and mean open times. The inhibitory effect of ONOO- could be overcome by reduced glutathione. Glutathione, added after ONOO-, restored whole cell current amplitude to control levels and reverted single-channel gating to control behavior. The inhibitory effect of ONOO- on membrane K+ current is consistent with its contractile effects in isolated cerebral arteries and single myocytes. Taken together, our data suggest that ONOO- has the potential to alter cerebral vascular tone by inhibiting BK channel activity.