title: Uptake of the 35 kDa major surfactant apoprotein (SP-A) by neonatal rabbit lung tissue.
abstract: Secreted surfactant is made up of both phospholipid and protein components. Therefore, we investigated the possibility that surfactant apoproteins might be taken up by the alveolar type II cell in a manner similar to the uptake of surfactant phosphatidylcholines. Day 2 neonatal rabbits were infused via the trachea with a solution of carrier surfactant and 125I-labelled surfactant apoprotein (SP-A, Mr approx. 35,000). Most of the 125I-SP-A remained within the alveolus; however, a fraction of the 125I-SP-A was taken up by the lung tissue from the alveolus in a time-dependent manner. The small amount of radiolabeled material detected in blood, liver or kidney tissues of 125I-SP-A-infused animals was not trichloroacetic acid (TCA) precipitable, i.e., probably represented degradation products. In contrast, the proportion of TCA-precipitable 125I-SP-A in lung tissue or lavage samples did not change as function of time after tracheal administration. Two-dimensional gel electrophoresis of the 125I-SP-A present in the lavage samples or associated with lung tissue was used to show that a small proportion of the 125I-SP-A was partially degraded in the lung tissue and alveolus. These data are suggestive that the SP-A is taken up by lung tissue, perhaps in a manner similar to the uptake of surfactant phospholipid by the alveolar type II cell.
authors.affiliation: Department of Cell Biology, University of Texas Health Science Center, Dallas.
authors.forename: J M
authors.initials: JM
authors.lastname: Snyder
authors.forename: H F
authors.initials: HF
authors.lastname: Rodgers
authors.forename: H C
authors.initials: HC
authors.lastname: Nielsen
authors.forename: J A
authors.initials: JA
authors.lastname: O'Brien
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D001992:Bronchoalveolar Lavage Fluid; D011232:Chemical Precipitation; D007668:Kidney / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D008168:Lung / Q000378:metabolism*; D008970:Molecular Weight; D011510:Proteolipids / Q000378:metabolism*; D011650:Pulmonary Alveoli / Q000378:metabolism; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000378:metabolism*; D011817:Rabbits; D012709:Serum Albumin / Q000378:metabolism; D014018:Tissue Distribution; D014238:Trichloroacetic Acid
chemical_list: D011510:Proteolipids; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; D012709:Serum Albumin; D015060:1,2-Dipalmitoylphosphatidylcholine; D014238:Trichloroacetic Acid