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The authors have studied the effects of free radical scavengers, superoxide dismutase (SOD) and extract of Ginkgo biloba (EGb 761, flavone-rich extract) on ion shifts (Na, K and Ca) induced by ischaemia and reperfusion in rat retina obtained from normotensive and spontaneously hypertensive rats. Eyes were subjected to 90 min of ischaemia by occlusion of the retinal artery, followed by 4 and 24 hours of reperfusion. SOD (15,000 U/kg, i.v.) or EGb 761 (50 mg/kg, per os) was administered in a daily dose for 10 days. In the drug-free control groups, 90 min of ischaemia significantly increased tissue Na gains from their pre-ischaemic control values of 63 +/- 7 microM/g dry weight (in retina obtained from normotensive rats) and 76 microM/g dry weight (in retina obtained from hypertensive rats) to 89 +/- 9 microM/g dry weight and 101 +/- 7 microM/g dry weight, respectively. During reperfusion, a further elevation was found in retinal Na in both the normotensive and hypertensive groups. Probably, because of the ischaemia-induced inhibition of Na-K-ATPase, retinal K loss was detected after ischaemia and reperfusion, respectively. An accumulation of retinal Ca was measured after ischaemia and reperfusion in the normotensive and spontaneously hypertensive groups. Both free radical scavengers significantly reduced the maldistribution of ions induced by ischaemia and reperfusion, but the effectiveness of drugs was more evident in normotensive than hypertensive groups.(ABSTRACT TRUNCATED AT 250 WORDS)