Pressure arteriograph

Ascending aortas (from the root to just distal to the innominate branch point) and left carotid arteries (from the transverse aorta to 6 mm up the common carotid) were dissected and mounted on a pressure arteriograph (Danish Myotechnology, Copenhagen, Denmark) in balanced physiological saline (130 mM NaCl, 4.7 mM KCl, 1.6 mM CaCl₂, 1.18 mM MgSO₄·7H₂O, 1.17 mM KH₂PO₄, 14.8 mM NaHCO₃, 5.5 mM dextrose, and 0.026 mM EDTA, pH 7.4) at 37 °C. Vessels were transilluminated under a microscope connected to a charge-coupled device camera and computerized measurement system (Myoview, Danish Myotechnology) to allow continuous recording of vessel diameters. Prior to data capture vessels were pressurized and stretched to in vivo length (Wagenseil et al., 2005 (link)). Intravascular pressure was increased from 0 to 175 mmHg in 25 mmHg steps. At each step, the outer diameter (OD) of the vessel was measured and manually recorded. Segmental distensibility was calculated from the pressure diameter curves as follows: distensibility (SD₂₅) over a 25 mmHg interval = [OD_{Higher Pressure (H)} − OD_{Lower Pressure(L)}]/OD_(L)/25 (Knutsen et al., 2018 (link)).

Following blood pressure measurement and euthanasia, ascending aorta and left common carotid artery were excised and placed in physiologic saline solution (PSS) composed of 130 mM NaCl, 4.7 mM KCl, 1.6 mM CaCl₂, 1.18 mM MgSO₄−7H₂O, 1.17 mM KH₂PO₄, 14.8 mM NaHCO₃, 5.5 mM dextrose, and 0.026 mM Ethylenediaminetetraacetic acid (EDTA, pH 7.4) overnight at 4°C. Vessels were cleaned of surrounding fat, mounted on a pressure arteriograph (Danish Myo Technology) and maintained in PSS at 37 °C. Vessels were visualized with an inverted microscope connected to a CCD camera and a computerized system, which allows continuous recording of vessel diameter. Intravascular pressure was increased from 0 to 175 mmHg by 25-mmHg increments, the vessel outer diameter was recorded at each step (12 s per step). The average of three measurements at each pressure was reported.

The left pulmonary artery (LPA), from the pulmonary trunk to just proximal to the first bifurcation, was excised post-euthanasia. Vessels were mounted on a pressure arteriograph (Danish Myotechnology, Copenhagen, Denmark) in balanced physiologic saline at 37°C, pressurized, and longitudinally stretched three times to in vivo length prior to data capture. Vessels were then transilluminated under a microscope connected to a charge-coupled device camera and computerized measurement system (Myoview, Danish Myotechnology) to allow for continuous recording of vessel diameters (further details on the pressure arteriography procedure can be found in (8 (link)). Intravascular pressure was increased from 0 to 70 mmHg in 10-mmHg steps. At each step, the outer diameter of the vessel was measured and manually recorded.