Pulmonary arterioles and capillaries

Pulmonary arterioles and capillaries represent the functional microvascular unit of the lung, primarily responsible for facilitating gas exchange between the alveolar air and the blood. Pulmonary arterioles are small resistance vessels that regulate blood flow through the lungs via vasoconstriction and vasodilation, while the capillaries form a dense network around alveoli to maximize the surface area for oxygen and carbon dioxide diffusion (StatPearls, 2023). These structures play a critical role in maintaining low-pressure circulation within the pulmonary system. Pathological changes in these vessels, such as endothelial dysfunction, medial hypertrophy, and plexiform lesion formation, are hallmarks of pulmonary arterial hypertension (PAH) (NIH, 2022). Such remodeling increases pulmonary vascular resistance, eventually leading to right-sided heart failure. While not a single molecular target, these vessels contain numerous therapeutic targets, including phosphodiesterase type 5 (PDE5), endothelin receptors, and prostacyclin receptors. Drugs like sildenafil and bosentan act on these specific molecular pathways within the arteriolar walls to induce vasodilation and inhibit pathological remodeling (PubMed, 2021). Consequently, the pulmonary microvasculature is the primary site of action for most vasoactive therapies used in treating pulmonary vascular diseases.

Other names

Pulmonary microvasculatureLung microvesselsPulmonary resistance vessels

Drugs targeting the pulmonary microvasculature primarily work by modulating the nitric oxide, endothelin, and prostacyclin pathways to induce vasodilation of the arteriolar smooth muscle and inhibit pathological vascular remodeling.