Cooper K E, Tang J M, Rae J L, Eisenberg R S
J Membr Biol. 1986;93(3):259-69. doi: 10.1007/BF01871180.
Patch-clamp recording from the apical surface of the epithelium of frog lens reveals a cation-selective channel after pressure (about +/- 30 mm Hg) is applied to the pipette. The open state of this channel has a conductance of some 50 pS near the resting potential (-56.1 +/- 2.3 mV) when 107 mM NaCl and 10 HEPES (pH 7.3) is outside the channel. The probability of the channel being open depends strongly on pressure but the current-voltage relation of the open state does not. With minimal Ca2+ (55 +/- 2 microM) outside the channel, the current-voltage relation is nonlinear even in symmetrical salt solutions, allowing more current to flow into the cell than out. The channel, in minimal Ca2+ solution, is selective among the monovalent cations in the following sequence K+ greater than Rb+ greater than Cs+ greater than Na+ greater than Li+. The conductance depends monotonically on the mole fraction of K+ when the other ion present is Li+ or Na+. The single-channel current is a saturating function of [K+] when K+ is the permeant ion, for [K+] less than or equal to 214 mM. When [Ca2+] = 2 mM, the current-voltage relation is linearized and the channel cannot distinguish Na+ and K+.
对蛙晶状体上皮细胞顶端表面进行膜片钳记录时发现，当向微电极施加压力（约±30毫米汞柱）后，会出现一个阳离子选择性通道。当通道外部为107毫摩尔/升氯化钠和10毫摩尔/升HEPES（pH 7.3）时，该通道在静息电位（-56.1±2.3毫伏）附近的开放状态电导约为50皮西门子。通道开放的概率强烈依赖于压力，但开放状态下的电流-电压关系则不然。当通道外部钙离子浓度极低（55±2微摩尔）时，即使在对称盐溶液中，电流-电压关系也是非线性的，流入细胞的电流比流出的更多。在钙离子浓度极低的溶液中，该通道对单价阳离子具有选择性，顺序为钾离子＞铷离子＞铯离子＞钠离子＞锂离子。当存在的另一种离子为锂离子或钠离子时，电导单调依赖于钾离子的摩尔分数。当钾离子为通透离子且钾离子浓度小于或等于214毫摩尔时，单通道电流是钾离子浓度的饱和函数。当钙离子浓度为2毫摩尔时，电流-电压关系线性化，通道无法区分钠离子和钾离子。
