Postnatal growth of the mammalian lung: lack of influence by carbon monoxide exposure

The growth and internal partitioning of the lung are increased in young animals exposed to high altitude. Neither the mechanism whereby O2 lack brings this about nor the anatomic site of action of hypoxia is known. To test whether extrapulmonary tissue hypoxia can stimulate lung growth in the prescence of normal alveolar PO2, pulmonary morphology was studied quantitatively in young rats exposed to 208 ppm carbon monoxide for 29-30 days. The results show no effect of this exposure on lung dimensions and thus argue against extrapulmonary tissue hypoxia as the relevant stimulus in the increased lung growth that occurs at high altitude.