Abstract

We studied the effects of a free-radical scavenger, EGb 761, on electrolyte shifts (Na+, Ca2+, and K+) induced by ischemia and reperfusion in the retinas obtained from streptozotocin-induced diabetic rats. Eyes were subjected to 90 min ischemia followed by 24 h of reperfusion by clamping and releasing the central retinal artery. Ten days before the induction of ischemia and reperfusion, diabetic rats received a daily dose of 25, 50, and 100 mg/kg p.o. of EGb 761, respectively (n = 12 in each group). In the drug-free diabetic control group, 90 min ischemia followed by 24 h of reperfusion resulted in an increase in retinal Na+ and Ca2+ (measured by atomic absorption spectrophotometry) compared to nonischemic control values of 73 +/- 4 and 2.6 +/- 0.3 mumol/g dry weight to 113 +/- 5 (p < 0.05) and 5.3 +/- 0.3 mumol/g dry weight (p < 0.05), respectively. Tissue K+ content was significantly reduced compared to its nonischemic diabetic control value of 268 +/- 7 to 213 +/- 6 mumol/g dry weight (p < 0.05). EGb 761 dose-dependently reduced reperfusion-induced ion imbalance, improving the recovery of ion content in diabetic rat retina. EGb 761 did not reduce blood glucose in streptozotocin-induced diabetic rats. Therefore we may conclude that these protective effects of EGb 761 are independent of blood glucose content or of the severity of diabetes and protect against electrolyte shifts directly in retinal cells.