4.7. Fabrication and Preparation of Rat Thoracic Aortic Rings

After anesthetizing Sprague–Dawley rats (6–7 weeks old) with urethane, the chests were immediately incised, and the thoracic aortas were removed. The extracted blood vessels were immediately supplied with a gas mixture of 95% O₂ and 5% CO₂ and maintained at 37 °C in Krebs–Henseleit solution (K–H solution, composition, mM: NaCl, 118.0; KCl, 4.7; MgSO₄, 1.2; KH₂PO₄, 1.2; CaCl₂, 2.5; NaHCO₃, 25.0; and glucose, 11.1; pH 7.4). The tissue and fat around blood vessels were removed, and the vessels were cut into rings approximately 2 mm in length. In experiments requiring the removal of the endothelium, the lumen of the vessel was removed by scraping with a thin cotton swab. The lower and upper parts of the fabricated thoracic aortas were hung with stainless steel hooks, the lower parst were connected to hooks installed on the bottom of the organ bath, and the upper parts were connected to an isometric force transducer connected to a physiograph to measure changes in isotonic contraction using PowerLab Chart 7.0 software (ADI instrument Co., Sydney, NSW, Australia) program. The aortic segments were stabilized in an organ bath, loaded with 1 g of passive tension, and stabilized for 1 h prior to the next experiment.