COMPARATIVE BIOCHEMISTRY OF GESTATIONAL AND POSTNATAL LUNG GROWTH ANDDEVELOPMENT IN THE RAT AND HUMAN

We compared the ontogeny of collagen (hydroxyproline), elastin (desmos ine), soluble protein, and DNA in the lungs of rats and humans during gestation and postnatal life. In humans, lung weight/body weight ratio s declined faster during gestation than postnatally, whereas in rats l ung weight/body weight ratio declined little during gestation and then suddenly on the first day of life. Lung weight/body weight ratios may be lower than expected around term in humans, and prediction data are given to assess human pulmonary hypoplasia. Rats and humans differed in water content of their lungs, with rats showing a sharper decline d uring gestation. In the human lung, collagen and elastin made their ap pearance at an early stage of gestation; elastin, in particular, incre ased rapidly during gestation, suggesting a role in intrauterine alveo lar formation. In the rat, elastin accumulation is primarily a postnat al event, as is alveolar formation. Hydroxyproline concentrations incr eased with conceptual age and continued to increase rapidly postnatall y between 4 and 7 weeks in the rat, but slowed in the human after 60 w eeks of conceptual age. Desmosine concentrations level off at the end of the study period in rats, while these are still increasing, althoug h slowly, in humans. Overall lung growth, as assessed by weight, was l inear in humans, but phases of lung growth were apparent in the rat, i ncluding one of minimal growth in the immediate postnatal period. (C) 1997 Wiley-Liss, Inc.