2.2. Measurement of Right-Ventricular Systolic Pressure (RVSP)

As previously described [36], rats were anesthetized with an intraperitoneal injection of xylazine (6 mg/kg) and ketamine (60 mg/kg). Through an incision in the neck, the trachea was exposed and cannulated with PE 240 tubing, and the rat ventilated in room air (~70–80 breaths/min). The chest was opened, PE 50 tubing with a small needle was inserted into the right ventricle, and the pressure was recorded on a Grass polygraph (model 7E). At the end of the pressure measurements, the lungs were perfused with autoclaved normal saline to remove blood. The left lung and the heart were placed in 10% buffered formaldehyde. The right lung was quickly frozen in liquid nitrogen and stored at −80 °C for transcriptomic analysis at a later date.