Quantification of surfactant pool sizes in rabbit lung during perinatal development.

Abstract

Methods are presented for the quantitative isolation of surfactants from fetal and newborn rabbit alveolar lavage returns and post-lavaged lung tissue homogenates. The phospholipid content of both fractions progressively increased between 27 days gestation and term (31 days). The tissue-stored fraction increased approximately 16-fold (from 0.48 +/- 0.13 to 7.83 +/- 0.86 mg/g dry lung) and the alveolar fraction more than 30-fold (from 0.08 +/- 0.02 to 2.69 +/- 0.52 mg/g dry lung). Developmental changes in phospholipid composition were also observed. Tissue-stored surfactant was prepared using differential and density gradient centrifugation. Alveolar surfactant was isolated during fetal development as a high-speed pellet following a one-step differential centrifugation. There was little change in the phospholipid content of fetal alveolar lavage supernatant (range 0.12 +/- 0.04 to 0.28 +/- 0.09 mg/g dry lung). By the first postnatal day the phospholipid content of both lavage fractions significantly increased (pellet, 7.51 +/- 1.79; supernatant, 4.01 +/- 1.36 mg/g dry lung) and both were identified as surfactant. This increase in alveolar surfactant was accompanied by an approximately twofold decrease (to 3.81 +/- 1.1 mg/g dry lung) in the tissue-stored fraction. These data provide a quantitative profile of surfactant accumulation and secretion in developing rabbit lung.