ABSTRACT
This study investigated the impact of experimental pulmonary arterial hypertension (PAH) progression by evaluating morphometric and functional parameters, oxidative stress, autonomic nervous system (ANS) activation, and inflammation in the right (RV) and left (LV) ventricles. Male rats were first divided into two groups: monocrotaline (MCT) and control. The MCT group received a single MCT injection (60 mg/kg, intraperitoneal), while control received saline. The MCT and control groups were further divided into four cohorts based on how long they were observed: 1, 2, 3, and 4 weeks. Animals were submitted to echocardiographic and hemodynamic analysis. RV and LV were used for morphometric, biochemical, and histological measurements. Autonomic modulation was evaluated by cardiac spectral analysis, considering two components: low frequency (LF) and high frequency (HF). Lung and liver weight was used for morphometric analysis. MCT induced 100% mortality at 4 weeks. In the RV, disease progression led to mild inflammation and enhanced reactive oxygen species (ROS) in week 1, followed by moderate inflammation, ROS production, and hypertrophy in week 2. By week 3, there was moderate inflammation, oxidative stress, and ANS imbalance, with development of right heart dysfunction. LV biochemical changes and inflammation were observed at week 3. The initial changes appeared to be related to inflammation and ROS, and the later ones to inflammation, oxidative stress, and ANS imbalance in MCT animals. This study reinforces the severity of the disease in the RV, the late effects in the LV, and the role of ANS imbalance in the development of heart dysfunction.