Protective Effects of Melatonin and Aminoguanidine on the Cornea in

Abstract

Purpose: This study was designed to investigate the protective effect of aminoguanidine (AG) and melatonin (M) on the cornea in a streptozotocin-induced diabetic rat model.

Methods: Twenty-eight Sprague-Dawley rats were used in this study. Animals were divided into 4 groups: control (C), diabetes (D), diabetes + AG (D+AG), and diabetes + M (D+M). Diabetes was induced by 1 intraperitoneal dose of 45 mg/kg of streptozotocin (STZ). In the treatment groups, the D + AG group received AG in their water (1 g/L), and D + M rats were injected with M (10 mg/kg/d) intraperitoneally. One of the groups remained an untreated diabetic group (D group). All animals were euthanized at the end of 8 weeks. After enucleation, eyes were fixed in 10% phosphate-buffered formalin and embedded in paraffin wax. Histochemical stains were applied, and specimens were examined under a light microscope.

Results: After 8 weeks, the rats in the diabetes group had significantly lower body weight and significantly higher blood glucose levels than those of the control, D + AG, and D + M groups. Diabetes resulted in prominent edema in the stroma with interruptions in the subepithelial basement membrane. These alterations were not prominent or were absent in the D + AG and D + M groups. The mean thicknesses of the cornea, corneal epithelium, and stroma were statistically significantly different between the C and D, and D and D + AG and D + M groups (P < 0.05).

Conclusions: Long-term administration of AG and M reduced corneal injury in an STZ-induced diabetic rat model. AG and M may be potential candidates in the treatment of diabetic keratopathies. However, further studies are needed to elucidate the mechanisms of the protective effect of both molecules on diabetic corneal complications.