Apical and basal endothelial nitric oxide release each regulate distinct subcellular functions within the vessel wall

Throughout the endothelium, endothelial nitric oxide synthase (eNOS) localizes to the plasma membrane, especially at the myoendothelial junction (MEJ), a discreet region located on the basal side where the endothelial cells (EC) and smooth muscle cells (SMC) make contact. We therefore hypothesized that the localized release of nitric oxide (NO) at the MEJ serves distinct functions compared to other compartments within the endothelium. Using isolated thoracodorsal (TD) resistance arteries and a vascular cell co‐culture (VCCC) model, we show that the EC specific agonist bradykinin (BK) phosphorylates eNOS at the apical membrane of EC monolayers, whereas the (SMC) specific agonist phenylephrine (PE) selectively phosphroylates eNOS only at the MEJ. PE significantly increased cGMP production in SMCs compared to BK, however NO x measurements from the buffer of isolated TD arteries or from the EC side of the VCCC showed that only BK stimulated a significant increase in NO x accumulation. We extended these observations by showing NO released from the EC monolayer inhibited leukocyte adherence, whereas PE stimulation did not. Our results demonstrate that eNOS at the MEJ likely serves to regulate vessel relaxation following constriction, whereas the apical pool regulates vessel dilation in response to EC agonists and inhibition of leukocyte adherence.