Role of calcium influx through voltage-operated calcium channels and of calcium mobilization in the physiology of Schistosoma mansoni muscle contractions
Role of calcium influx through voltage-operated calcium channels and of calcium mobilization in the physiology of Schistosoma mansoni muscle contractions
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DOI：
10.1017/s0031182006000023
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发表时间：
2006-07-01
期刊：
影响因子：
2.4
通讯作者：
Day, T. A.
中科院分区：
文献类型：
--
作者：
Mendonca-Silva, D. L.;Novozhilova, E.;Day, T. A.
我们测试的假设，电压操作的Ca 2+通道介导的细胞外Ca 2+内流的肌纤维从人类寄生虫曼氏血吸虫，沿着Ca 2+动员从肌浆网，有助于肌肉收缩。事实上，全细胞电压钳显示由二价离子携带的电压门控内向电流，其峰值电流由+20 mV（从-70 mV的保持电位）的阶跃引起。升高的细胞外K+引起的纤维去极化引起的收缩完全依赖于细胞外Ca 2+，并被尼卡地平抑制（在4（.）1 μ M）。然而，这些收缩对电压门控Ca 2+通道的其他经典阻断剂不是非常敏感，表明与哺乳动物对应物相比，溶酶体肌肉通道具有非典型药理学。此外，5 mM咖啡因诱导的收缩被抑制后，耗尽的肌浆网无论是毒胡萝卜素（10 μ M）或ryanodine（10 μ M）。提示电压操纵性Ca ~（2+）通道参与了S. mansoni收缩以及储存的Ca 2+的动员，尽管在平滑肌中肌浆网的体积小。
We tested the hypothesis that voltage-operated Ca2+ channels mediate an extracellular Ca2+ influx in muscle fibres from the human parasite Schistosoma mansoni and, along with Ca2+ mobilization from the sarcoplasmic reticulum, contribute to Muscle contraction. Indeed, whole-cell voltage clamp revealed voltage-gated inward currents carried by divalent ions with a peak current elicited by steps to + 20 mV (from a holding potential of -70 mV). Depolarization of the fibres by elevated extracellular K+ elicited contractions that were completely dependent on extracellular Ca2+ and inhibited by nicardipine (half inhibition at 4(.)1 mu M). However these contractions were not very sensitive to other classical blockers of voltage-gated Ca2+ channels, indicating that the schistosome Muscle channels have an atypical pharmacology when compared to their mammalian counterparts. Furthermore, the contraction induced by 5 mM caffeine was inhibited after depletion of the sarcoplasmic reticulum either with thapsigargin (10 mu M) or ryanodine (10 mu M). These data suggest that voltage-operated Ca2+ channels docontribute to S. mansoni contraction as does the mobilization of stored Ca2+, despite the small volume of sarcoplasmic reticulum in schistosome smooth muscles.