This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The manifestations of pulmonary artery hypertension (PAH) are nonspecific and the course variable, creating a need for reliable parameters to guide clinical decision making. Simple biochemcial tests would be useful to diagnose and assess the progress of the disease. There is increasing evidence that plasma B-type natriuretic peptide (BNP) may be a useful marker for dysfunction of the right ventricle associated with a rise in pulmonary artery pressure. In addition, the investiagors have determined that the lungs can synthesize and release macrophage migration inhibitory factor (MIF), a factor that causes cardiac dysfunction. MIF is known to be associated with hypoxia. Recently, the invesetigators have also found a putative natural inhibitor of MIF (ISO-nat). The investigators hypothesize that baseline plasma BNP and MIF are surrogate markers of clincal severity of PAH and that changes in plasma BNP and MIF levels pre and post exercise (six-minute walk test) will correlate with severity of disease.