Mathias R T, Rae J L, Eisenberg R S
Biophys J. 1979 Jan;25(1):181-201. doi: 10.1016/S0006-3495(79)85284-4.
The electrical properties of the crystalline lens of the frog eye are measured with stochastic currents applied with a microelectrode near the center of the preparation and potential recorded just under the surface. The stochastic signals are decomposed by Fourier analysis into sinusoidal components, and the impedance is determined from the ratio of mean cross power to input power. The data are fit by an electrical model that includes two paths for current flow: one through the cytoplasm, gap junctions, and outer membrane; the other through inner membranes and the extracellular space between lens fibers. The electrical properties of the structures of the lens which appear as circuit components in the model are determined by the fit to the data. The resistivity of the extracellular space within the lens is comparable to the resistivity of Ringer. The outer membrane has a normal resistance of 5 kohm . cm(2) but large capacitance of 10 muF/cm(2), probably because it represents the properties of several layers of fibers. The inner membranes have properties reminiscent of artificial lipid bilayers: they have high membrane resistance, 2.2 megohm . cm(2), and low specific capacitance, 0.8 muF/cm(2). There is so much membrane within the lens, however, that the sum of the current flow across all the inner membranes is comparable to that across the outer surface.
用微电极在靠近标本中心处施加随机电流，并在标本表面正下方记录电位，以此测量蛙眼晶状体的电学特性。通过傅里叶分析将随机信号分解为正弦分量，并根据平均交叉功率与输入功率之比确定阻抗。数据由一个电学模型拟合，该模型包括两条电流通路：一条通过细胞质、缝隙连接和外膜；另一条通过内膜和晶状体纤维之间的细胞外空间。模型中表现为电路元件的晶状体结构的电学特性由与数据的拟合确定。晶状体内细胞外空间的电阻率与林格液的电阻率相当。外膜的正常电阻为5 kohm·cm²，但电容很大，为10 μF/cm²，这可能是因为它代表了几层纤维的特性。内膜具有类似于人工脂质双层的特性：它们具有高膜电阻，2.2 megohm·cm²，和低比电容，0.8 μF/cm²。然而，晶状体内有如此多的膜，以至于所有内膜上的电流总和与外表面上的电流总和相当。
