Experimental hypoxia of STZ-diabetic rat myocardium and protective effectsof Ginkgo biloba extract - II. Ultrastructural investigation of microvascular endothelium

Four months after induction of diabetes by intraperitonal injection of 60 m g streptozotocin/ kg body weight wistar rats were exposed to an acute respi ratoric hypoxia of 20 min duration. One group of the rats received daily Gi nkgo biloba extract EGb, 761 (100 mg/kg body weight). By means of qualitati ve and quantitative electron microscopic analysis we compared the hypoxia-i nduced ultrastructural alterations of the myocardial microvascular endothel ium in normal, diabetic, and EGb-protected rats. Aim of the study was to co mpare the hypoxia tolerance of myocardial microvessels of normal and diabet ic rats and to test the possibility of antioxidative protection. The results revealed that only some ultrastructural microvascular parameter s of diabetic rats were stronger altered after acute hypoxia than normal on es, e.g. capillary dilatation, number of lysosomes, frequency of vesicles a nd fused vesicles, endothelial swelling, and structural state of mitochondr ia. Other parameters exhibited less severe alterations than in healthy rats , as luminal blebbing and protrusions, endothelial vacuoles, mitochondrial swelling, and pericapillary debris. Protective effects of EGb could be demo nstrated on endothelial swelling, blebbing, vesiculation and vesicular fusi oning, partly on vacuolization, but not on mitochondrial parameters. The re sults were discussed on pathobiochemical background. EGb 761 was estimated to be protective against hypoxic damage on myocardial microvessels also in diabetic condition, but the study should be completed by inclusion of a reo xygenation interval.