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Recently identified, angiopoietin‐1 (Ang1) and ‐2 (Ang2) bind to the tyrosine kinase receptor Tie2 and contribute to orchestrate blood vessel formation during angiogenesis. Ang1 mediates vessel maturation and integrity by favoring the recruitment of pericytes and smooth muscle cells. Ang2, initially identified as a Tie2 antagonist, may under certain circumstances, induce Tie2 phosphorylation and biological activities. As inflammation exists in a mutually dependent association with angiogenesis, we sought to determine if Ang1 and/or Ang2 could modulate proinflammatory activities, namely P‐selectin translocation, in bovine aortic endothelial cells (EC) and dissect the mechanisms implicated. P‐selectin, an adhesion molecule found in the Weibel‐Palade bodies of EC, is translocated rapidly to the cell surface upon EC activation during inflammatory processes. Herein, we report that Ang1 and Ang2 (1 nM) are capable of mediating a rapid Tie2 phosphorylation as well as a rapid and transient endothelial P‐selectin translocation maximal within 7.5 min (125% and 100% increase, respectively, over control values). In addition, we demonstrate for the first time that angiopoietin‐mediated endothelial P‐selectin translocation is calcium‐dependent and regulated through phospholipase C‐γ activation.

Sarafotoxin 6c S6c is a specific agonist for the endothelinB ETBreceptor, being largely used as a standard compound in pharmacological studies related to ETBreceptors. We have developed an improved peptide synthesis procedure. Using the Fmoc chemistry methodology and an appropriate orthogonal protection scheme, we obtained a crude peptide with a major component identified as CysAcm1.15S6c. A silver salt AgBF4treatment of this crude material completely removed the Acm moieties without the appearance of any major sideproducts. The free peptide was cyclized using a Fe3Fe2oxidizing method. Besides the formation of the bridges, no other modification was observed. Thus, the peptide purification was facilitated and an excellent yield of pure sarafotoxin was obtained. The material was characterized by analytical reverse phasehigh performance liquid chromatography RPHPLC and matrix assisted laser desorption ionizationtime of flight MALDITOF mass spectrometry. Pharmacological properties of the peptide were evaluated in an ETBpreparation guinea pig lung parenchyma strips and were identical to those of an S6c standard.

Actions of endothelin ET are usually mediated through the socalled endothelinA or B ETAor ETBreceptors. As part of our ongoing research program, we are studying the characterization of the ETAreceptor using specific photolabile ligands. Starting with the ETAspecific antagonist TTA386 as a leading compound we developed new ETAspecific antagonists containing the photolabile amino acid, pbenzoylphenylalanine Bpa. Following a Bpa peptide scan, with either the L or Disomer, we found that Dphenylalanine6 of TTA386 can be substituted with either L or DBpa and gives analogs showing antagonistic properties, in an ETAreceptor preparation rat aorta, very similar to those of TTA386 itself. No agonistic or antagonistic properties were measured with these derivatives in an ETBpharmacological preparation guinea pig lung parenchyma. Thus, these new ligands appear as very promising probes for the characterization of the ETAreceptor.