Ang-1 is produced by pericytes and smooth muscle cells ( Figure 1 ). In the glomerulus, which lacks pericytes, Ang-1 is produced by podocytes [61] . Ang-1 has a high affinity for the extracellular matrix, and so circulating levels do not reflect tissue levels, which in part is probably responsible for the constitutive phosphorylation of Tie2 in quiescent endothelium [62] [63] [64] [65] . Ang-2 is produced in ECs and stored in Weibel-Palade bodies (WPBs) [66, 67] . The release of Ang-2 from WPBs by exocytosis can be regulated independently of the release of other stored proteins [68] . Tie2 is expressed predominantly by ECs, although some subsets of macrophages and multiple other cell types express Tie2 at low levels [69, 70] . In ECs, Tie2 is most abundant in the endothelial caveolae [71] .