A histological study of changes in the lingual papillae of streptozotocin-induced diabetic rats

This study examined the effect of experimental diabetes mellitus on the dorsal tongue of rats which were made diabetic by tail-vein injections of streptozotocin (50 mg/kg) and then raised for either 5 or 10 months. Lingual papillae were observed by scanning electron microscopy (SEM) and light microscopy. Morphological changes in lingual mucosal capillaries in 10-month diabetic rats were observed by electron microscopy (TEM). In the study of cellular movement in the lingual dorsal epithelium, bromodeoxyuridine (BrdU) was applied as a tracer for studying DNA replication. In diabetic rats, lingual papillae showed morphological atrophic changes. The lingual mucosal capillaries' alterations included endothelial cells with numerous cell projections into the lumen, degenerated cell organs, increased basement membrane width, and narrowed capillary lumen. BrdU labeling index among the basal cells was reduced in diabetic rats which indicates a possible retardation of their epithelial-tissue activity. In diabetes mellitus, direct metabolic disturbances to the epithelia because of insulin deficiency first occurred, successively diabetic microangiopathy appeared on the lingual mucosal capillaries. The appearance of diabetic microangiopathy caused tissue hypoxia, which induced atrophic changes to the epithelia.