Labeling of phosphatidylcholine in the alveolar wash of rabbits in utero.

Radioactive palmitic acid, choline, and phosphate were given to rabbits 28 and 30 days pregnant and the labeling;of phosphatidylcholine in the fetal lung and alveolar wash was studied. Labeled phosphatidylcholine was detected initially in the alveolar wash three hours after isotope administration. The three-hour delay was independent of precursor studied or gestational age, and the radioactive phosphatidylcholine continued to accumulate in the wash fluid for at least 18 hours. Each labeled precursor of phosphatidylcholine sequentially labeled the phosphatidylcholine from microsomal, lamellar body and alveolar wash lung fractions of the 30 day fetal animals.