EFFECT OF VITAMIN-A-DEFICIENCY ON THE ADHESION OF RAT CORNEAL EPITHELIUM AND THE BASEMENT-MEMBRANE COMPLEX

Purpose. To understand the underlying mechanisms responsible for the e asy removal and sloughing of corneal epithelium in vitamin A deficienc y. Methods. An animal model of vitamin A deficiency, the vitamin A-def icient rat (A- rat), transmission electron microscopy, computer-assist ed morphometric analysis and indirect immunofluorescence were used to study the adhesion of rat corneal epithelium to its basement membrane with emphasis on structure and molecular composition of the anchoring structures such as the hemidesmosome and bullous pemphigoid antigen. R esults. Transmission electron microscopy resolved numerous microsepara tions of the basal epithelial cell membrane from the basement membrane with intervening segmental basement membrane duplications and electro n dense deposits. Morphometric analysis disclosed a statistically sign ificant reduction in the frequency and size of hemidesmosomes. Four we eks after supplementing the diet with retinyl acetate (700 mug/week), significant reversal of these same structural abnormalities could be d etected. Immunofluorescence staining for bullous pemphigoid antigen, a component of the adhesion complex, showed intense staining of the bas al epithelial cytoplasm but weak and discontinuous staining of the bas ement membrane. Weak staining for laminin was also evident in A- corne as. In contrast, normal corneas displayed no cytoplasmic staining for bullous pemphigoid antigen and intense staining of the basement membra ne for bullous pemphigoid antigen and laminin. Conclusions. The author s propose that structural abnormalities of the epithelial basement mem brane complex are responsible for the observed loose epithelial adhesi on and sloughing, as well as other known abnormalities of healing in t he vitamin A-deficient rat cornea.