Effects of streptozotocin-induced type 1 diabetes mellitus on protein and ion concentrations in ocular tissues of the rat

Abstract

This study investigated the effects of streptozotocin (STZ)-induced diabetes mellitus (DM) on protein and cation levels inocular tissues (lenses, cornea, lacrimal glands and retina with sclera) of rats. Diabetic rats and their lacrimal glands weighedsignificantly less (p < 0.05) than age-matched controls. Diabetic animals also had significantly (p < 0.05) elevated bloodglucose and significantly reduced (p < 0.05) plasma insulin compared to controls. Total protein concentrations in the cornea,lens, lacrimal gland and retina with sclera were markedly reduced compared to controls (circa 50%-90%). Diabetic cornea,lenses, lacrimal glands, and retina with sclera contained more Ca2+ (p < 0.05) than age-matched controls (2-3 fold). Levels ofZn2+ were also elevated (p < 0.05) in the cornea and retina with sclera of diabetic rats, as compared to control rats (2-3 fold),but were unaffected in lenses and lacrimal glands. In contrast, levels of Cu2+, Mg2+, Na+ and K+ were significantly reduced (p< 0.05) in all ocular tissues of diabetic rats when compared to control animals (circa 30%-70%). These results show thatSTZ-induced DM is generally associated with significant physiochemical changes in ocular tissues of rats with changesobserved in body weight, blood glucose, and insulin levels and protein and cation concentrations compared to healthy agematchedcontrols. Based on these data, it has been speculated that diabetes may induce changes in ocular tissues that include:higher protein turnover through increased protease activity and changes in Na+ / K+ channel function. It is suggested thatthese changes may be associated with diabetic retinopathy, diabetic cornea and sight impairment. (Int J Diabetes Metab13:154-158, 2005)