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Diabetes impairs the opening of collateral vessels in patients with cardiac ischemia, and this participates to the poor prognosis of coronary vessel disease in patients with diabetes. We have studied the effect of hyperglycemia on the development of coronary vessels in the model of the chick embryo. Material and methoids: Hyperglycemia was induced at the eighth day of incubation by a single intravitellous injection glucose, 5mg/g whole egg. Control embryos received either mannitol(M) or sterile water matched for osmolarity and volume, respectively. The coronary vessels were analyzed by coronarography, immunohistochemistry and quantitative-PCR. Results: The development of coronary vessel coronary vessels was altered by hyperglycemia, as assessed by the number of coronary arteries crossing a fixed line on digitalized images of angiographies performed by day 7 of hyperglycemia (21 vs 35 in control embryos; n=6 in each group, p<0.05). On histological sections, the number of intra-myocardial arterioles (stained by an anti-smooth muscle actin antibody); 23/10[sup 5] pixel² vs 42 (p<0.01) was decreased as well as that of capillaries (stained by a lectin): 124/10[sup 5] pixel² vs 183 (p<0.01). By day 3 post-hyperglycemia, the expression of HIF-2 alpha and that of VEGF were decreased, as assessed by quantitative PCR Conclusion: During embryonic development, hyperglycemia alters the formation of both epicardic and intra-myocardic vessels. [ABSTRACT FROM AUTHOR]