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.
Highlights
On density gradient centrifugation of the banded material, the bulk of this fraction again banded at the interface between the sucrose layers, but a small pellet was always present
Further density gradient centrifugations resulted in no further removal of material from the banded fraction
Several methods involving differential and density gradient centrifugation have been developed for isolating surfactant fractions from alveolar lavage returns andlor lung tissue homogenates [12]
Summary
30-fold (from 0.08 f 0.02 to 2.69 f 0.52 mg/g dry lung). Developmental changes in phospholipid composition were observed. * * in the phospholipid content of fetal alveolar lavage supernatant (range 0.12 0.04 to 0.28 0.09 mg/g dry lung). * significantly increased (pellet, 7.51 f 1.79; supernatant, 4.01 1.36 mg/g dry lung) and both were identified as surfactant.This increasein alveolar surfactant was accompanied by an approximately twofold decrease (to 3.81 + 1.1 mg/g dry lung) in the tissue-stored fraction. Lung surfactant is a phospholipid-rich material that lines the mammalian lung and prevents atelectasis by reducing the surface tension at the air-alveolar interface [1]. Surfactant is synthesized in the alveolar Type I1 cell and stored in intracellular lamellar inclusion bodies prior to release to the alveoli ( 5 )
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