Among numerous biologically important molecules produced by the vascular endothelium, nitrogen oxide (NO) has a particularly important function in cardiovascular homeostasis. This presentation will mostly focus on the role of two kinases, Akt and AMP-activated kinase (AMPK), in endothelial NO-production. Akt or protein kinase B is a serine/threonine phosphokinase which is a downstream effector of phosphoinositide 3-kinase (PI3-K)dependent signalling pathways. It is involved in endothelial functions, including activation of endothelial NO-synthase (eNOS) and promotion of endothelial cell survival. We have found that the G-protein activators histamine and thrombin inhibit EGF mediated endothelial Akt phosphorylation. The implications relate to the role of Akt in maintaining structural and functional integrity of vascular endothelium. Its role in activating eNOS is particularly important. To our surprise we found that both histamine and thrombin stimulate eNOS phosphorylation and NO-production. Examination of potential kinases that could mediate such PI3K-Akt independent activation of eNOS led to the discovery of AMPK as a key player in the pathway. AMPK has been called a metabolic masterswitch because of its central role in regulating cellular energy balance. As an activator of endothelial NO production it may provide a link between metabolic demand and blood flow. Most recently our work has been aimed at defining upstream mechanisms of AMPK activation in endothelial cells resulting in the identification of two kinases that are involved. LKB1 is activated by a rise in AMP/ATP ratio and the calcium/calmoduline kinase kinase is activated by the calcium spike evoked by the G-protein-phospholipase C-inositol trisphosphate cascade.