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The lungs play an important role in the metabolism of vasoactive substances including endogenous amines. The role of pulmonary clearance of circulating norepinephrine has not been well defined in the young lamb (7-8 d of age). Using radiolabeled tracer norepinephrine in acutely instrumented lambs, we determined the in vivo pulmonary clearance and spillover rate of norepinephrine under baseline and hypoxic conditions. The fractional extraction of norepinephrine, the percent removed on a single pass through the pulmonary circulation, was 23 +/- 2%. The corresponding pulmonary clearance rate was 61 +/- 10 mL/kg/min and the net pulmonary norepinephrine removal rate was 0.41 +/- 0.14 nmol/kg/min. This clearance represented over 70% of whole body norepinephrine clearance. The spillover of synaptic norepinephrine was 0.22 +/- 0.13 nmol/kg/min. During hypoxia, animals showed significant increases in pulmonary artery pressure and resistance. Fractional extraction and norepinephrine decreased to 16 +/- 3%, p less than 0.005. Pulmonary clearance decreased to 31 +/- 7 mL/kg/min, and net pulmonary norepinephrine removal rate decreased to 0.27 +/- 0.07 nmol/kg/min. These results demonstrate that pulmonary clearance plays a significant role in norepinephrine clearance in 1-wk-old lambs. Alteration of norepinephrine clearance during physiologic states such as hypoxia may be important in the pathophysiology of altered pulmonary vascular resistance in newborn animals.
B A Chappell, and
J F Padbury, and
D M Habib, and
A M Martinez, and
S L Thio, and
E E Burnell, and
J A Humme
July 1997,
The American journal of physiology,
B A Chappell, and
J F Padbury, and
D M Habib, and
A M Martinez, and
S L Thio, and
E E Burnell, and
J A Humme
December 2004,
British journal of anaesthesia,
B A Chappell, and
J F Padbury, and
D M Habib, and
A M Martinez, and
S L Thio, and
E E Burnell, and
J A Humme
August 1986,
The American review of respiratory disease,
B A Chappell, and
J F Padbury, and
D M Habib, and
A M Martinez, and
S L Thio, and
E E Burnell, and
J A Humme
November 1978,
Pediatric research,
B A Chappell, and
J F Padbury, and
D M Habib, and
A M Martinez, and
S L Thio, and
E E Burnell, and
J A Humme
January 1974,
Comptes rendus des seances de la Societe de biologie et de ses filiales,
B A Chappell, and
J F Padbury, and
D M Habib, and
A M Martinez, and
S L Thio, and
E E Burnell, and
J A Humme
January 1990,
Pediatric research,
B A Chappell, and
J F Padbury, and
D M Habib, and
A M Martinez, and
S L Thio, and
E E Burnell, and
J A Humme
January 1993,
Journal of applied physiology (Bethesda, Md. : 1985),
B A Chappell, and
J F Padbury, and
D M Habib, and
A M Martinez, and
S L Thio, and
E E Burnell, and
J A Humme
January 1991,
Life sciences,
B A Chappell, and
J F Padbury, and
D M Habib, and
A M Martinez, and
S L Thio, and
E E Burnell, and
J A Humme
September 1997,
Circulation research,
B A Chappell, and
J F Padbury, and
D M Habib, and
A M Martinez, and
S L Thio, and
E E Burnell, and
J A Humme
November 1989,
The American journal of physiology,
