Body growth, lung and heart weight, and DNA content in newborn rats exposed to different levels of chronic hypoxia.

To evaluate the contribution of maternal factors in the somatic underdevelopment of newborns exposed to chronic hypoxia we took advantage of the observation that, in the rat, daily changes of the mother did not alter the normal postnatal growth of the litter. Body growth and heart and lung development were studied in (a) normoxic litters nursed either by normoxic mothers or by mothers exposed to 24 h of hypoxia on alternate days, and (b) litters growing in hypoxia and raised by mothers which were either hypoxic at all times or normoxic on alternate days. From the results it is concluded that neonatal growth retardation during moderate (15% O2) or severe (10% O2) hypoxic exposure can be almost entirely attributed to the effects of hypoxia on the newborn, and is not mediated by the maternal response. Mild (19% O2) or moderate levels of 1-week hypoxic exposure had little or no inhibitory effects on somatic and lung growth, while cardiac weight and DNA content increased. Severe hypoxia (10% O2) resulted in important growth retardation with hypoplasia (decreased weight and DNA content) of heart and lungs, although the negative effects on the growth of these organs were not as marked as those of the extrapulmonary and extracardiac tissues.