Pulmonary hypoxic vasoconstriction: not affected by chemical sympathectomy.
The influence of chemical sympathectomy with 6-hydroxydopamine (6-OHDA) on regional alveolar hypoxic vasconstriction and on global hypoxic pulmonary vasoconstriction was investigated. In eight dogs a double-lumened endotracheal tube allowed ventilation of one lung with nitrogen as an alveolar hypoxic challenge while ventilation of the other lung with 100% O2 maintained adequate systemic oxygenation. Distribution of perfusion to the two lungs was determined with 133Xe and external counters. Mean perfusion to the test lung was 50.9 +/- 4.9% of total lung perfusion on room air and decreased by 32.4% (P smaller than 0.01) during alveolar hypoxia. Following 6-OHDA the test lung continued to reduce perfusion during alveolar hypoxia by 27.3%. In five dogs global hypoxia induced a 106% increase in pulmonary vascular resistance (PVR) prior to 6-OHDA and a 90% increase in PVR after 6-OHDA. After 6-OHDA no rise in PRV or systemic blood pressure occurred in response to tyramine, confirming effective sympathectomy by the 6-OHDA. Thus, sympathectomy with 6-OHDA failed to substantially block regional alveolar hypoxic vasoconstriction or global hypoxic pulmonary vasconstriction.
D000818:Animals; D004285:Dogs; D006892:Hydroxydopamines / Q000494:pharmacology*; D008168:Lung / Q000098:blood supply* / Q000294:innervation; D009584:Nitrogen; D010100:Oxygen; D012119:Respiration; D013564:Sympathetic Nervous System / Q000187:drug effects; D014661:Vasoconstriction / Q000187:drug effects*; D014980:Xenon Radioisotopes
D006892:Hydroxydopamines; D014980:Xenon Radioisotopes; D009584:Nitrogen; D010100:Oxygen