Angiotensin II receptors in Xenopus oocytes.
Angiotensin II receptors in Xenopus oocytes.
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非洲爪蟾卵母细胞中的血管紧张素 II 受体。
DOI：
10.1098/rspb.1991.0044
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发表时间：
1991
期刊：
影响因子：
--
通讯作者：
Miledi,R
中科院分区：
文献类型：
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作者：
Woodward,RM;Miledi,R
用电记录的方法研究了异种卵母细胞对八肽血管紧张素II(ALL)的敏感性。所有激动剂均可引起与膜电导增加相关的振荡电流。来自不同蛙类的卵母细胞对ALL的反应性差异很大，而来自同一卵巢的卵母细胞之间的反应性差异较小。敏感性较高的青蛙卵母细胞的反应阈值在0.5~1.0 nM之间，在-6 0 mV的保持电位下，对电流大于3μA的1μm ALL有反应，而有些蛙卵母细胞对ALL无反应，甚至对10μm ALL也没有反应。共有79只青蛙的618个卵母细胞被测试对ALL的敏感性，85%的青蛙卵母细胞有可检测到的电反应。ALL诱发的振荡氯电流在很大程度上不依赖于细胞外钙离子，可被EGTA螯合细胞内钙离子所消除，并可被卵母细胞内注射三磷酸肌醇(IP3)所模拟。除了振荡的氯离子电流外，它们还引起细胞外钙离子的内流，在膜的超极化步骤上产生瞬时的内向氯离子电流。这些实验都表明，所有的反应都是通过激活由肌醇磷脂水解所触发的细胞内信使通路，肌醇多磷酸动员细胞内的钙离子，以及激活钙门控的氯离子通道来实现的。用9个不同的实验记录了70个去卵泡的卵母细胞，研究了人工或酶促去卵泡对所有反应的影响。用扫描电子显微镜检测去卵泡程序的效果，证实可去除90%至98%以上的卵泡细胞。在所有的情况下，所有的反应都在去卵泡过程中基本保留下来，这表明所有介导膜电流反应的受体都位于卵母细胞本身，而不是卵泡细胞。
Electrical recordings were used to study the sensitivity of nativeXenopusoocytes to the octapeptide angiotensin II (All). All elicited oscillatory currents associated with an increase in membrane conductance to Cl-. Responsiveness to All varied greatly between oocytes taken from different frogs, and to a lesser extent between oocytes from the same ovary. Oocytes from frogs showing high sensitivity had response thresholds between 0.5-1.0 nM All, and at a holding potential of – 60 mV, responded to 1 μm All with currents greater than 3 μA. In contrast, oocytes from some frogs gave no response, even to 10 μm All. A total of 618 oocytes from 79 frogs were tested for sensitivity to All, and oocytes from 85% of frogs gave detectable electrical responses. Oscillatory Cl-currents elicited by All were largely independent of extracellular Ca2+, were abolished by chelation of intracellular Ca2+using EGTA and were mimicked by intraoocyte injection of inositol 1, 4, 5 - trisphosphate (IP3). In addition to oscillatory Cl-currents, All also evoked an influx of extracellular Ca2+, giving rise to a transient inward Cl-current on membrane hyperpolarizing steps. These experiments all suggested that All responses were elicited through activation of an intracellular messenger pathway triggered by hydrolysis of inositolphospholipids, mobilization of intracellular Ca2+by inositol polyphosphates, and activation of Ca2+- gated Cl-channels. The effect of manual or enzymic defolliculation on All responses was studied in nine separate experiments recording from 70 defolliculated oocytes. Efficacy of defolliculation procedures was assayed using scanning electron microscopy, which confirmed removal of 90 to greater than 98% of follicular cells. In all cases All responses were substantially preserved through defolliculation, suggesting that the All receptors that mediate membrane current responses are located in the oocyte itself, and not in follicular cells.