Dynamic changes of fenestrations in choriocapillaries.

Abstract

The ultrastructure of choriocapillaries from dark-adapted eyes of Uroloncha Striata Domestica was studied with a freeze-fracture replica technique. Fenestrations were observed on the surface of the cleavage plane of the choriocapillary endothelial membrane. Fenestrations of endothelial cells facing Bruch's membrane in controls were densely distributed and clearly separated from the non-fenestrated areas. The average diameter of the fenestrations was 71±6 nm and the average number of fenestrations was 39.1±6.0/μm2. In the dark-adapted eye, the fenestrations of endothelial cells facing Bruch's membrane were scattered and it was impossible to clearly distinguish the fenestrated areas from non-fenestrated areas. The average diameter of the fenestrations was 70±6 nm and the average number of fenestrations was 27.4±7.6/μm2. The difference in fenestration density between control and adapted eyes was significant (P<0.01). These findings indicate that the distribution pattern of fenestrations in endothelial cells of choriocapillaries is dynamic and results in a decrease in vascular permeability of the choriocapillaries in the dark.