NPY regulates human endocardial endothelial cell function

Growing evidence suggests that endocardial endothelial cells (EECs) may play an important role in the regulation of cardiac function by releasing several cardioactive factors such as endothelin-1 (ET-1), Angiotensin II (Ang II) and nitric oxide (NO). In our laboratory, we demonstrated that similar to ET-1, EECs do possess different types of NPY receptors, specifically Y1 and Y2 receptors. Furthermore, activation of these receptors was found to increase the steady-state level of intracellular free Ca2+ in EECs and the frequency of beating of cardiomyocytes. In addition, NPY was also found to be present in EECs, and an increase of steady-state intracellular free Ca2+ induced the release of this peptide from these cells. Thus, similar to ET-1, NPY seems to be released from EECs and this peptide seems to regulate excitation–secretion of these cells as well as excitation–contraction coupling of ventricular cardiomyocytes.