Thyroid hormones, malnutrition, and biochemical composition of developing rat lung.

We studied the effects of thyroid hormones and malnutrition on protein, DNA, and phospholipid content of the developing rat lung during the first month of life. Neonatal hypothyroidism significantly decreases the lung phospholipid content by 30-45% between 5 and 30 days of age whether the results are expressed per milligram DNA or per gram tissue. Administration of thyroxine for 3 days to hypothyroid rats increases significantly (20%) their total phospholipid content, mainly through its preferential effect on phosphatidylcholine (50% increase). Adult animal response to thyroid hormones is markedly different from that observed in young rats for most parameters examined. In malnourished rats, lung tissue phospholipids are decreased per cell but not per unit cell mass after 11 days of age. These results show that hypothyroidism has a specific effect on lung phospholipids during the neonatal period.