LANTHANUM AND PROCION YELLOW AS EXTRACELLULAR MARKERS IN THE CRYSTALLINE LENS OF THE RAT

When rat lenses are incubated in La(NO3)3 or Procion yellow containing salt solutions at 37°C, the markers enter the lens extracellular space as determined by electron microscopy and fluorescence microscopy respectively. Nearly continuous tracks of either marker can be found between each epithelial cell whether the incubations are done by totally immersing the lenses in solution in a single chamber or by isolating the anterior and posterior lens surfaces so that only a small portion of the anterior surface contacts the marker containing solution. Counting of specialized junctions associated with lens epithelial cells in thin sections, shows that less than 20% of these cells have junctions associated with their lateral borders, either near the anterior pole of the lens or near the equator. Junctions between epithelial cells and lens fibers occur more frequently near the equator than anteriorly. It is concluded that the extracellular space between rat lens epithelial cells is not sealed off by zonulae occludentes and that morphologic markers are free to move in the channels between these cells. It is further suggested that the well known physiologic barrier at the anterior side of the lens is not associated directly with the lens epithelium. Procion yellow does not enter the nuclear extracellular space even after eight hours of incubation although it is ubiquitously distributed throughout the cortical extracellular space. © 1979.