Jia M, Ehrenstein G, Iwasa K
Laboratory of Biophysics, National Institute of Neurological and Communicative Disorders and Stroke, Bethesda, MD 20892.
Proc Natl Acad Sci U S A. 1988 Oct;85(19):7236-9. doi: 10.1073/pnas.85.19.7236.
Parathyroid cells have unusual responses to an increase in the external calcium concentration--a reduction in secretion and a depolarization. In an attempt to explain this behavior, we have studied voltage-clamped inside-out patches from bovine parathyroid cells. We found a potassium-selective channel that requires internal calcium to open and has a 175-pS conductance. This channel differs from calcium-activated potassium channels that have been found in other cells in that it closes when the internal calcium concentration is increased above about 160 nM. This channel can account for the depolarization that occurs in parathyroid cells in high-calcium solutions. It may also account for the reduced secretion in high-calcium solutions.
甲状旁腺细胞对外界钙浓度升高有异常反应——分泌减少和去极化。为了解释这种行为，我们研究了来自牛甲状旁腺细胞的电压钳制内向外膜片。我们发现了一种钾选择性通道，它需要细胞内钙来打开，电导为175皮西门子。该通道与在其他细胞中发现的钙激活钾通道不同，当细胞内钙浓度增加到约160纳摩尔以上时它会关闭。该通道可以解释高钙溶液中甲状旁腺细胞发生的去极化。它也可能解释高钙溶液中分泌减少的原因。
