Abstract
Purpose: :
To determine the effects of acute hyperglycemia on the retinal circulation and endothelial function of retinal arteries.
Methods: :
Ten adult cats were used in this study. Anesthesia was induced in each animal with sevoflurane. Glucose (50%) was infused continuously from the femoral vein catheter to maintain the plasma glucose concentration at 5 mmol/L (normoglycemia [NG] group) or 30 mmol/L (hyperglycemia [HG] group) for 3 hours. Vessel diameter and blood velocity were measured simultaneously in the large retinal arterioles using laser Doppler velocimetry and the retinal blood flow (RBF) was calculated. To investigate the effects of hyperglycemia on endothelial function in the retinal arterioles, we evaluated the response of the retinal arterioles to endothelium-dependent vasodilator bradykinin (BK) or endothelium-independent vasodilator sodium nitroprusside (SNP), which was injected intravitreously.
Results: :
Three hours after glucose infusion, the vessel diameter, blood velocity, and RBF were unchanged in the NG group (n=5) but increased by 18.4±1.7%, 46.2±4.3%, and 83.4±5.8%, respectively, compared with baseline in the HG group (n=5). In the NG group, BK increased the vessel diameter (35.5±4.1%), blood velocity (50.2±4.8%), and RBF (134.5±5.3%), whereas BK significantly decreased the vessel diameter (6.8±2.1%), blood velocity (12.3±3.6%), and RBF (31.4±4.5%) (p<0.01) in the HG group compared with the NG group. There was no difference between both groups in the responses of all parameters to intravitreous injection of SNP.
Conclusions: :
Acute hyperglycemia significantly reduced the endothelial-dependent BK-induced increase in vessel diameter, blood velocity, and RBF, suggesting that acute hyperglycemia may induce endothelial dysfunction of the retinal arteries.
Keywords: retina • diabetes • diabetic retinopathy