Electrical properties of structural components of the crystalline lens

Abstract

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.