Abstract

Pulmonary vascular responsiveness to norepinephrine(NE), angiotensin-II (ANG-II), acetylcholine(ACh) and nitroglycerin (NG) was examined in isolated perfused rat lungs. The lungs were perfused with pyridoxalated hemoglobin polyoxyethylene conjugate (PHP), a newly introduced modified hemoglobin, stroma free hemoglobin (SFH) or hydroxyethyl starch (HES) at a constant flow rate. Perfusion pressure (PP) and intra-tracheal pressure (ITP) were measured. Effects of intrapulmonary arterial injection of NE, ANG-II, ACh and NG on PP were examined. NE and ANG-II produced a dose dependent increase in PP in all groups. The response to NE in PHP or SFH perfused group was significantly greater than that in HES-perfused group. ACh induced a dose dependent decrease in PP in HES and PHP groups, while in the SFH group, ACh produced a dose dependent increase in PP. NG produced a dose dependent decrease in all groups. Results showed that stroma free hemoglobin (SFH) inhibits relaxation induced by endothelium-derived relaxation factor (EDRF), but PHP dose not exert inhibitory action on vascular relaxation induced by EDRF.

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