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Effect of Beta Adrenergic Stimulation and Blockade on Intrapulmonary Arteriovenous Anastamoses Recruitment
Author(s) -
Bates Melissa,
Jacobson Joseph,
Hotter Jessica,
Eldridge Marlowe
Publication year - 2013
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.27.1_supplement.718.7
Subject(s) - propranolol , vasodilation , medicine , cardiac output , hypoxia (environmental) , stimulation , anesthesia , hemodynamics , blockade , endocrinology , chemistry , receptor , oxygen , organic chemistry
Intrapulmonary arteriovenous anastomoses (IPAVs) are large diameter conduits that bypass the pulmonary circulation. IPAVs can be recruited in humans by catecholamines and it has been suggested that this occurs as a result of an elevated cardiac output. In contrast, we hypothesized that IPAVs recruitment occurs as a result of beta adrenergic‐mediated vasodilation. To test our hypothesis, we measured the transpulmonary passage of 2.5×10 5 venous‐injected microspheres (25–50 μm) in anesthetized, room air ventilated rats infused with either saline (n=6) or isoproterenol (n=6) and found substantial microsphere passage in the isoproterenol group (0.4±0.9% vs 10.5±15.2%, p=0.007). However, because the contributions of cardiac output and vasodilation cannot be isolated in the intact model, we also perfused isolated rat lungs with buffered hetastarch (n=6) or isoproterenol (n=9), taking care to match pulmonary artery pressure and flow between groups. Transpulmonary microsphere passage occurred only in isoproterenol perfused lungs (1±3 vs 200±278, p=0.001). This suggests that, contrary to previous conclusions, catecholamines recruit IPAVs independently of increases in cardiac output, through active vasodilation. In subsequent preliminary work, we hypothesized that catecholamines are necessary for full IPAVs recruitment by hypoxia. In rats ventilated with 10% O 2 , pre‐treatment with propranolol (n=4) decreased the passage of microspheres by 58% compared to controls (n=5) (14.7±25.0 vs 6.1±3.2, p=0.10) but did not abolish the response. This suggests that the response to hypoxia is multifactorial, but that catecholamines are important contributors to IPAVs recruitment in hypoxia.