Studies on the permeability of the blood-retinal barrier I. on the existence, development, and site of a blood-retinal barrier

Abstract

The permeability of the retinal vessels of rabbits, cats, and rats to trypan blue and colloidal carbon was studied and compared with that of other vessels of the body. It was found that the retinal vessels, in common with those of the brain, showed a characteristic impermeability to these substances, which points to the existence in the retina of a Blood-Retinal Barrier, comparable to the well-known Blood-Brain Barrier. This barrier to trypan blue and colloidal carbon was also found to be present at a very early stage in the immature retinal vessels of the kitten, ratling, and young rabbit. In order to elucidate this problem, an attempt was made to relate the electron microscopical appearance of the vessels studied to their permeability to carbon and trypan blue. It was found that only two possible anatomical sites could be involved, namely the endothelial cells and the attachments between them, and it was shown that a particular type of tight junctional complex exists between the retinal endo-thelial cells.