Hyperglycemia is a major risk factor for endothelial dysfunction and vascular disease, and in the current study, the link to glucose-induced abnormal intracellular Ca²⁺ (Ca_i²⁺) homeostasis was explored in bovine aortic endothelial cells in high glucose (HG; 25 mmol/l) versus low glucose (LG; 5.5 mmol/l; control). Transient receptor potential 1 (TRPC1) ion channel protein, but not TRPC3, TRPC4, or TRPC6 expression, was significantly increased in HG versus LG at 72 h. HG for 4, 24, and 72 h did not change basal Ca_i²⁺ or ATP-induced Ca_i²⁺ release; however, the amplitude of sustained Ca_i²⁺ was significantly increased at 24 and 72 h and reduced by low concentration of the putative, but nonspecific, TRPC blockers, gadolinium, SKF-96365, and 2-aminoethoxydiphenyl borate. Treatment with TRPC1 antisense significantly reduced TRPC1 protein expression and ATP-induced Ca²⁺ entry in bovine aortic endothelial cells. Although the link between HG-induced changes in TRPC1 expression, enhanced Ca²⁺ entry, and endothelial dysfunction require further study, the current data are suggestive that targeting these pathways may reduce the impact of HG on endothelial function.