ULTRASTRUCTURAL EXAMINATION OF CORNEAL EPITHELIUM OF SPONTANEOUSLY OBESE, HYPERGLYCEMIC RATS

Purpose. Otsuka Long-Evans Tokushima fatty (OLETF) rats spontaneously become obese and hyperglycemic with age. We investigated whether the d evelopment of hyperglycemia would alter the ultrastructure of the corn eal epithelium. Methods. Scanning and transmission electron microscopy (SEM and TEM) were used to examine the morphology of corneal epitheli al cells. Fourteen OLETF rats were evaluated, and 9 Long-Evans Tokushi ma Otsuka (LETO) rats were used as control. Non-hyperglycemic OLETF ra ts served as controls. Results. SEM showed exfoliative changes in the surface of the central corneal epithelium of the hyperglycemic OLETF r ats. These superficial epithelial cells were irregular in shape as com pared to polygonal shapes of those of LETO and non-hyperglycemic OLETF rats. The mean anterior surface area of individual superficial epithe lial cells was significantly smaller in the hyperglycemic OLETF than t hat of the LETO or the non-hyperglycemic OLETF rats. Central protrusio n(s) could be found in some of the superficial cells of all rats exami ned, although this phenomenon was more common in the hyperglycemic rat s than in the non-hyperglycemic rats. TEM revealed that there were num erous cytoplasmic vacuoles and wide intercellular spaces in the centra l corneal epithelium of the hyperglycemic OLETF rats, but not in the n on-hyperglycemic rats. Conclusions. The development of spontaneous hyp erglycemia in OLETF rats alters the ultrastructure of the corneal epit helium. The alterations included abnormalities of the corneal epitheli al surface observed by SEM and the presence of intracellular vacuoles and enlarged intercellular spaces detected by TEM.