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R.A. Akhtar, H. Zhang; Effects of High Glucose and Streptozotocin–Induced Diabetes on Cell Proliferation and Protein Kinase C Activity in Rat Corneal Epithelium . Invest. Ophthalmol. Vis. Sci. 2005;46(13):887.
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Purpose: Diabetic patients are prone to delayed corneal epithelial wound repair following vitrectomy and keratectomy. The purpose of this work was to investigate the effects of high glucose on cell proliferation and protein kinase C (PKC) activity in cultured corneal epithelial cells. We also examined whether streptozotocin–induced diabetes has any effect on PKC activity in rat corneal epithelium. Methods:Serum–starved, primary rat corneal epithelial cells (RCEC) were cultured in media containing different concentrations of glucose. After 24 hrs, the cultures were terminated and the cells trypsinized and either counted for determination of cell proliferation or used for analysis of PKC activity. Sprague Dawley rats (200–250 g) were made diabetic by an iv injection of streptozotocin (65 mg/kg BW). After 4 weeks of confirmed diabetes, the corneal epithelial tissue was removed from diabetic and non–diabetic rats and used for PKC assay. Results: RCEC exhibited a large increase in their proliferation when cultured for 24 hrs in a medium containing 7.8 mM glucose (low glucose). Increasing glucose concentration to 37 mM (high glucose) resulted in a significant decrease in proliferation of the cells. Under the same experimental conditions, there was a significant increase in PKC activity in RCEC cultured in high glucose medium as compared to the control cells cultured in low glucose medium. When analyzed for PKC activity in corneal epithelium, a significant increase in translocation of PKC activity from soluble to the particulate fraction was observed in the diabetic rats as compared to the non–diabetic rats. Conclusions: The data demonstrate that high glucose inhibits RCEC proliferation but stimulates PKC in these cells. Activation of PKC under diabetic conditions suggests a complex role for this enzyme in delayed epithelial wound repair in diabetic cornea.
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