Morphological evidence for the transfer of anionic macromolecules from the interior of the eye to the blood stream.

We have either introduced into the vitreous space or perfused through the anterior chamber of macaque monkey eyes two anionic tracers, anionic ferritin (AF) and horseradish peroxidase (HRP) and a cationic probe, cationic ferritin (CF). We have observed that the anionic molecules, but not the cationic one, are transported to the blood stream by plasmalemmal vesicles of the endothelial cells in both the retinal and the iridial vasculature. We suggest that a variety of organic anions of different MW which are commonly present in the eye tissues may be returned to the blood by the same morphological mechanism.