Effects of Vanadate on Glucose Metabolism in the Streptozotocin-Diabetic Rat Lens

Minoru Endo, Masao Nagata, Kazuhiko Adachi and Akihiko Tamai

Department of Ophthalmology, Faculty of Medicine, Tottori University, Yonago 683, Japan

The effects of oral administration of vanadate, an oxidized form of vanadium, on glucose metabolism of the lens were studied in 5-week-old male Sprague-Dawley rats rendered diabetic with streptozotocin (50 mg/kg, intraperitoneal injection). One week later, the diabetic rats were given 0.2 g/L NaV0₃-5 g/L NaCl solution in drinking water ad libitum for 2 weeks and the biochemical parameters in their lenses were determined. Blood glucose levels significantly decreased in the vanadate-treated diabetic rats (diabetic, vanadate-treated group: DV group), compared with the diabetic rats given no vanadate (diabetic, control group: D group). In the DV group, significant decreases were observed in lens contents of glucose and sorbitol with a tendency to decrease in lens fructose content, compared with the D group. In the former group, aldose reductase activity did not decrease, but sorbitol dehydrogenase (SDH) activity significantly increased, compared with the latter group. These results suggest that oral administration of vanadate may decrease the sorbital content in the diabetic rat lens by an acceleration of the sorbitol pathway to fructose conversion accompanied by an increase in SDH activity.

Key words: aldose reductase; diabetic rat lens; sorbitol; sorbitol dehydrogenase; vanadate

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