SOD1 and pulmonary arterial hypertension: In contrast, only the antioxidant enzyme catalase becomes activated in some (Ecarnot-Laubriet et al., 2003) but not all studies (Pichardo et al., 1999) while SOD and glutathione peroxidase are not activated at all in the compensated stage of RV hypertrophy secondary to pulmonary hypertension, predisposing the RV to ROS induced damage at an earlier stage than in the LV (Pichardo et al., 1999; Ecarnot-Laubriet et al., 2003; Schreckenberg et al., 2015).