LUNG GROWTH IN HYPOBARIC NORMOXIA, NORMOBARIC HYPOXIA, AND HYPOBARIC HYPOXIA IN GROWING RATS .1. BIOCHEMISTRY

Adaptive changes in cellular and connective tissue components of the l ung after chronic exposure to reduced ambient oxygen and/or pressure w ere studied. Four-week-old male Sprague-Dawley rats were randomly divi ded into five groups (n = 12 each): 1) general control, room air (GC); 2) hypobaric normoxic; 3) normobaric hypoxic; 4) hypobaric hypoxic; a nd 5) weight-matched control, restricted food intake (WMC; weight matc hed to hypobaric hypoxic animals). Lung growth (lung weight and DNA, R NA, protein, hydroxyproline, and desmosine contents) diminished in WMC compared with GC. Somatic growth decreased in hypobaric and normobari c hypoxic rats compared with GC. Lung weight; DNA, RNA, protein, hydro xyproline, and desmosine contents; and RNA/DNA, protein/DNA, and desmo sine/DNA ratios increased in both hypobaric and normobaric hypoxic rat s compared with WMC. Hydroxyproline and desmosine contents and the hyd roxyproline/DNA ratio were significantly higher in hypobaric than norm obaric hypoxic rats. Hypobaric normoxia caused a slight somatic growth reduction, but biochemical parameters of lung growth remained unaffec ted. In conclusion, in growing animals, despite inhibition of lung gro wth due to reduced food consumption, accelerated lung growth in hypoba ric or normobaric hypoxia occurs by hyperplastic and hypertrophic chan ges. Hypobaric normoxia does not affect lung growth, but connective ti ssue proteins accumulate slightly more in hypobaric hypoxia than in hy poxia alone.