Hyperglycemia-induced endothelial dysfunction is generally believed to be the basis of diabetic vascular complications. Dopamine receptors is known to play an important protective role in diabetes. However, the protective effect of dopamine receptors against hyperglycemia-induced endothelial damage in diabetic rats is still unknown. In the present study, we established a cell model of hyperglycemia-induced endothelial dysfunction by treating human umbilical vein endothelial cells (HUVEC) with high glucose. MIT and lactate dehydrogenase assays results showed that high glucose treatment significantly reduced the cell viability and down-regulated dopamine D-4 receptor. Pre-treatment with PD168077, a specific D-4 receptor agonist, greatly improved endothelial cell viability and decreased apoptosis. Furthermore, pharmacological inhibition of phosphoinositide 3-kinase (PI3K) and endothelial nitric oxide synthase (eNOS) eliminated the protective effect of D-4 receptor against endothelial injury. More importantly, the expression level of D-4 receptor was also dramatically down-regulated in the arterial endothelium of rats with streptozotocin-(STZ)-induced diabetes, and the STZ-induced impairment of acetylcholine-induced vasodilation was reversed by activation of D-4 receptor. In conclusion, our results indicated that dopamine D-4 receptor protected against hyperglycemia-induced endothelial dysfunction via the PI3K/eNOS pathway, which may provide a novel strategy in the treatment of diabetes. (C) 2019 Elsevier Inc. All rights reserved.