Blood-aqueous barrier in newborn and young rabbits. An electron microscopic study

Distribution of intravenously injected horseradish peroxidase (HRP) in the ciliary body of newborn and young (2 weeks old) rabbits was studied with the electron microscope. The reaction product was localized in all animals in the lumen of the blood vessels, in the perivascular area, in the surrounding connective tissue stroma and also in the epithelial cell layers. The peroxidase penetrated through the intercellular junctions of the pigmented cells to the intercellular space between the apical membranes of the two epithelial cell layers. In young rabbits peroxidase penetrated between the apical intercellular clefts of the non-pigmented cells in small quantities only, whereas in the newborn animals the clefts were filled with peroxidase. This reflects differences in the blood-aqueous barrier mechanism between the two studied groups and is evidently due to developmental stages of the eyes.