Fort 10

Changes in vasomotor tone of aortic tissues in response to adenosine were recorded in organ chambers. The thoracic aorta was carefully removed, cleaned of fat and connective tissue, and cut into 5–6 mm rings. Rings were suspended in Krebs-Henselheit solution with the following composition (mM): NaCl 118, KCl 4.7, KH₂PO₄ 1.2, MgSO₄ 1.1, CaCl₂ 2.5, NaHCO₃ 25 and glucose 5.5; pH 7.4, maintained at 37 °C and continuously aerated with 95 % O₂, 5 % CO₂ for isometric tension recording in organ chambers. In some rings, endothelium was mechanically removed. The rings were connected to isometric tension transducers (Fort 10, World Precision Instruments) coupled with a digital recording system (PowerLab 8SP, ADInstruments). The completeness of endothelial denudation was confirmed by the absence of relaxation to the endothelial-dependent agonist acetylcholine (1 µM). After a 90-min equilibration period under a resting tension of 2 g, rings were constricted with 0.1 µM norepinephrine, and vasorelaxant responses to adenosine were determined in endothelium-denuded rings. When indicated, rings were previously incubated for 60 min either with vehicle (control) or the NO synthase inhibitor N^G-monomethyl-l-arginine (L-NMA; 10 µM).