The physiological mechanisms leading to the differentiation of blood vessels and the molecular pathophysiology of vessel- specific diseases are currently not well understood. Patients with diabetes have an increased risk of peripheral arterial disease. HEY2 is a stable marker gene for arterial, whereas COUP-TFII is highly expressed in venous endothelial cells. For COUP-TFII, a role in the glucose/insulin metabolism has been suggested in vivo. In order to analyze the underlying mechanism in vitro, HUAECs were maintained in 22.2 mM glucose medium and stimulated in a time (24, 48, 72 h)- and dose (0, 5, 50 nM)-dependent manner with insulin. In these cells, mRNA (by RT-PCR) and protein expression (by Western blot) of HEY2 and COUP-TFII was quantified. HEY2 showed no significant changes in mRNA or protein expression in response to insulin under these conditions. Furthermore, there was no significant impact on COUP-TFII mRNA expression. However, COUP-TFII protein level was increased after 72 h in a dose-dependent manner, compared to time-matched control (control: 100±11%, 5 nM insulin 186±10%, 50nM insulin 238±8%). In conclusion, our data suggest a stabilization of the venous marker protein COUP-TFII in arterial endothelial cells after long-term stimulation with insulin. In contrast, the arterial marker HEY2 did not change.