Abstract 12369: Synchrotron Radiation Coronary Microangiography Could Confirm Induction of Coronary Vasoconstriction by Cold Exposure in the Diabetic Rat

Abstract

Background: Previous reports have suggested that sympathetic nerve stimulation by cold exposure induces coronary vasoconstriction in diabetes, but this has not been directly confirmed. The purpose of this study was to confirm, in the in vivo diabetic rat, that coronary vasoconstriction is induced by cold exposure. Conventional coronary angiography cannot visualize small arteries of less than 300 μm in diameter, such as the rat coronary artery. We have developed a system of synchrotron radiation coronary microangiography (SRCA) in the in vivo rat. SRCA can visualize vessels as small as 50 μm in diameter, thus enabling us to evaluate the coronary artery reaction in the in vivo rat. Method: The advantages of synchrotron radiation-derived X-rays are their high spatial resolution (9 μm/pixel) obtained as a result of the increased photon density and straightness of the beam. Diabetes was induced in rats by administration of 65 mg/kg streptozotocin. A polyethylene tube for angiography was inserted into the carotid artery of anesthetized rat. SRCA was performed before and after cold exposure. We compared the changes in the caliber of the coronary arteries of normal rats (n = 6) with those of the diabetic rats (n = 6). Results: High spatial and density resolution images were obtained (Figure). Several points along the left coronary artery were measured in each rat. The coronary diameter after cold exposure was increased by 8.6% in the normal rats and decreased by 10% in the diabetic rats; the difference between the 2 groups was significant (p < 0.05). The measured points were divided into 3 categories according to diameter: small (< 150 μm), medium (150-250 μm), and large (> 250 μm). In each category of the normal rats, the coronary arteries were dilated. On the other hand, in each category of the diabetic rats, they were constricted. Conclusion: The SRCA system could confirm that sympathetic nerve stimulation by cold exposure induced coronary vasoconstriction in the in vivo diabetic rat.