The blood-aqueous barrier in five species.

The in vivo sites of the blood-aqueous barrier were determined in five animal species, using acriflavine neutral (224 mol. wt.), ultrafreezing and drying, fluorescence microscopy, and fluorometry. Not toxic, acriflavine had specific in vivo affinity for nuclear DNA and RNA, produced intense fluorescence, and did not pass through hematic barriers. Acriflavine was given in doses to produce the same concentrations in the systemic blood or in the aqueous humor. The exact sites of the blood-aqueous barrier, demonstrated by tracing the acriflavine fluorescence through tissues and individual cells, were in the basal cell membranes of inner ciliary and iridial epithelia and apical cell membranes of iridial and corneal endothelia. Acriflavine passed freely from the aqueous humor into the blood stream. It also followed an aqueous flow into the vitreous body and optic nerve head vessels. Interruption or reversal of this flow may cause open-angle glaucoma.