2008). Although ETB receptors expressed in smooth muscle cells is contributed to vasoconstriction (Pernow et al. 1996), their primary contribution to vascular tone in the coronary circulation is not well characterized. In contrast, ETB receptors in endothelial cells have beneficial effects on the vascular wall by clearing ET‐1 from plasma and stimulating the vasodilator nitric oxide (NO) generation (Shetty et al. 1993; Hynynen and Khalil 2006). Therefore, the elevated ET‐1 and ET receptors induced by CIH can lead to the negative cardiovascular sequelae of OSA patients (Wang et al. 2013). Here, EDN1 is linked to obstructive sleep apnea syndrome.