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

Four months after induction of diabetes by intraperitonal injection of 60 mg streptozotocin/kg body weight wistar rats were exposed to an acute respiratoric hypoxia of 20 min duration. One group of the rats received daily Ginkgo biloba extract EGb 761 (100 mg/kg body weight). By means of qualitative and quantitative electron microscopic analysis we compared the hypoxia-induced ultrastructural alterations of the myocardial microvascular endothelium in normal, diabetic, and EGb-protected rats. Aim of the study was to compare the hypoxia tolerance of myocardial microvessels of normal and diabetic rats and to test the possibility of antioxidative protection. The results revealed that only some ultrastructural microvascular parameters of diabetic rats were stronger altered after acute hypoxia than normal ones, e.g. capillary dilatation, number of lysosomes, frequency of vesicles and fused vesicles, endothelial swelling, and structural state of mitochondria. 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 demonstrated on endothelial swelling, blebbing, vesiculation and vesicular fusioning, partly on vacuolization, but not on mitochondrial parameters. The results 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 reoxygenation interval.