When injected into rats in a single subcutaneous or intraperitoneal administration, MCT undergoes hepatic transformation by cytochrome P450 monooxygenase in the liver to form MCT pyrrole, which causes muscular hypertrophy of the media of pulmonary vessels and leads to PAH and RV hypertrophy (24). Here, CYP20A1 is linked to pulmonary arterial hypertension.