Junctional permeability measurements in the embryonic chick lens

The purpose of this paper is two-fold: to measure junctional permeability of different types of dissociated lens cells and to compare the junctional permeability of dissociated lens cells to that of cells in the intact lens. Dissociated embryonic chick lens cells and intact embryonic chick lenses were loaded with the fluorescent dye 5,6 carboxyfluorescein diacetate. The return of fluorescence after bleaching an individual cell was used to estimate cell-to-cell permeability. Use of the confocal microscope facilitated quantitation of the return of fluorescence as well as optical sectioning needed to measure cell-to-cell permeability in an intact lens. Two types of dissociated cells were studied: spherical and short elongated cells. The average rate constant for 5,6 carboxyfluorescein transfer between these cells was 7.9 x 10(-3) sec-1 and 8.1 x 10(-3) sec-1, respectively. The junctional permeability for both types of cells was reduced by lowering internal pH to 6.0 by bathing the cells in a sodium acetate solution. Permeability measurements of the central epithelial cells of an isolated whole lens gave an average rate constant of 2.6 x 10(-3) sec-1, comparable to the rates measured in the dissociated cells. These results establish that the photobleach method can be used in intact lens to quantitatively assess junctional permeability and that dissociated epithelial cells have very nearly the same junctional permeabilities as cells in the intact lens.