JUNCTIONAL PERMEABILITY MEASUREMENTS IN THE EMBRYONIC CHICK LENS

The purpose of this paper is two-fold: to measure junctional permeabil ity of different types of dissociated lens cells and to compare the ju nctional permeability of dissociated lens cells to that of cells in th e intact lens. Dissociated embryonic chick lens cells and intact embry onic chick lenses were loaded with the fluorescent dye 5,6 carboxyfluo rescein diacetate. The return of fluorescence after bleaching an indiv idual cell was used to estimate cell-to-cell permeability. Use of the confocal microscope facilitated quantitation of the return of fluoresc ence as well as optical sectioning needed to measure cell-to-cell perm eability in an intact lens. Two types of dissociated cells were studie d: spherical and short elongated cells. The average rate constant for 5,6 carboxyfluorescein transfer between these cells was 7.9 x 10(-3) s ec(-1) and 8.1 x 10(-3) sec(-1), respectively. The junctional permeabi lity for both types of cells was reduced by lowering internal pH to 6. 0 by bathing the cells in a sodium acetate solution. Permeability meas urements of the central epithelial cells of an isolated whole lens gav e 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 as sess junctional permeability and that dissociated epithelial cells hav e very nearly the same junctional permeabilities as cells in the intac t lens. (C) 1996 Academic Press Limited