Pulmonary hypertension
Three major pathways are involved in abnormal proliferation and contraction of the smooth-muscle cells of the pulmonary artery in patients with pulmonary arterial hypertension. These pathways correspond to important therapeutic targets in this condition and play a role in determining which of three classes of drugs—endothelin receptor antagonists, phosphodiesterase type 5 inhibitors, and prostacyclin derivatives—will be used.