Increased synthesis of phosphatidylcholine by rat lung following premature birth

Pregnant rats were delivered prematurely at 20 days and 21 days gestation (2 and 1 day premature). The survival was 52 +/- 3% at 20 days gestation and 100% at 21 days gestation. [Me-14C]Choline incorporation into phosphatidylcholine increased by 60% during the 3 h of survival after delivery at 20 days gestation. The increase in incorporation occurred during the first hour of survival. [Me-14C]Choline incorporation also increased to a lesser extent following survival at 21 days gestation. The incorporation after 3 h of survival at 20 days and 21 days gestation was similar to that obtained with adult lung slices. The incorporation of [U-14C]glycerol, D-[U-14C]glucose, [1-14C]palmitate and [1,2-14C]ethanolamine did not increase following delivery at either 20 days or 21 days gestation. The incorporation of 33PO4 into phosphatidylcholine increased to the same relative extent as [me-14C]choline incorporation. D-[1-14C]Glucose incorporation into the fatty acid portion of phosphatidylcholine and triacylglycerols and oxidation to 14CO2 decreased during the 3 h of survival. The pattern of D-[U-14C]glucose incorporation following survival at 20 and 21 days gestation is similar to that obtained with adult lung slices. Dexamethasone treatment of mothers at 17 and 18 days gestation caused [Me-14C]choline incorporation to increase to adult values at 20 days gestation but not at 19 days or 21 days. We conclude that an adaptive mechanism exists which produces specific biochemical changes in lung metabolism following premature birth. This mechanism is functional in the rat as early as 2 days prior to normal term.