THE EFFECTS OF CHRONIC HYPOXIA ON THE PHARMACOLOGICAL RESPONSIVENESS OF THE PULMONARY-ARTERY

Chronic hypoxia (CH) is associated with several cardiopulmonary disord ers. In vitro and in vivo studies have established the morphological c hanges, but yielded conflicting results about the functional changes i nduced by CH in the pulmonary vascular bed. CH increases the responsiv eness to endothelium-dependent vasodilators in perfused lungs; however , in artery rings, a reduction is found in endothelium-dependent vasod ilation. In CH, vasoconstriction induced by endothelin-l is enhanced a nd vasodilation produced by atrial natriuretic peptide and Kf channel openers is increased. Vasoconstriction produced by acute hypoxia can b e either enhanced or reduced by CH, depending on the experimental prot ocol. An understanding of the functional changes associated with CH is particularly important for a rational approach to the treatment of di sorders associated with CH.