A permeability defect of the retinal pigment epithelium. Occurrence in early streptozocin diabetes
W. M. Kirber, C. W. Nichols, P. A. Grimes, A. I. Winegrad and A. M. Laties
The permeability of the blood-retina barrier was tested in rats with early
streptozocin-induced diabetes. Two different tracer substances were used:
fluorescein sodium and horseradish peroxidase (HRP). After intravenous
administration, the ocular distribution of fluorescein was studied by
fluorescence microscopy of freeze-dried tissue. A permeability defect of
the pigment epithelium to fluorescein was present in one half of the rats
four weeks after induction of diabetes. The dye entered the pigment
epithelial cells but could not be detected among the photoreceptors. The
only dyd visible in neural retina was within the retinal blood vessels. For
HRP, no fault whatsoever in the blood retina barrier was found: there was
no increase of vesicular uptake by the pigment epithelial cells; the tight
junctions between pigment epithelial cells were intact as were those
between the endothelial cells of retinal blood vessels.
