Protein deprivation from the neonatal period impairs lung development in the rat.
The effects of early protein-deficiency on lung development were studied in the rat. Newborn male rats were nursed in groups of eight. Control dams and pups received a 15% protein diet during the whole experiment. Test mothers only received 12 and 8% proteins from the 7th and the 14th day of lactation. Test rats fed a diet of 8% protein were weaned at 21 days and maintained on the low protein diet for 1 month. This caused a marked decrease in body weight gain, but lung/body weight ratio was not affected. Lung DNA and protein content, lung protein concentration, but not lung DNA concentration were decreased, suggesting the presence of fewer and smaller cells than in control lungs. Volume-pressure curves were performed on excised lungs. With air-filling, the curve obtained in rats fed a diet with 8% proteins was shifted downward and to the right, even when expressed as percent of maximal volume. Its exponential analysis assessed a decrease in lung compliance. In contrast, with saline-filling, the recoil pressure was decreased in rats fed a diet with 8% proteins. Both with air and saline-filling, the pressure at lung rupture was increased in malnourished rats. It is concluded that protein-deficiency from the neonatal period increases surface forces, decreases tissue elastic forces, and augments resistance of the lung to rupture.