| Abstrakt: |
Lavage from normal adult rabbit lung and two known derived fractions, Fraction T and Fraction S, were subjected to either differential ultracentrifugation in 1.090 g/ml KBr or sucrose density gradient ultracentrifugation; the surface activity of the lipid extract of selected fractions was measured. In differential ultracentrifugation, the three starting materials yielded a pellicle containing > 85% of the phospholipid with <1% protein. In sucrose density gradient ultracentrifugation: pulmonary washing, containing about equal weights of phospholipid and protein (60% albumin, 20% sIgA, 10% IgG, 10% minor proteins), produced one single band at density 1.040, containing virtually one single protein, namely >80% of the total sIgA (protein T) and up to 60% of the total phospholipid, whereas all the albumin and IgG were found at very low densities, 1.010 and 1.025, respectively; Fraction T, having nearly equal weights of one signle protein, sIgA, and phospholipid, produced two contiguous bands at densities 1.059 and 1.078, totalling >85% of its phospholipid and <25% of its protein, the balance of which was found free of phospholipid at densities 1.020 to 1.050; comprising >80% of the phospholipid and <20% of the protein of pulmonary washing, Fraction S yielded two small bands at densities 1.028 and 1.044 and a major band at d=1.059. In surface activity measurements: when the total lipid extract of the bands from the sucrose density gradient ultracentrifugation was spread as a film, in spite of similarly high dipalmitoyl lecithin contents (about 70% palmitoyl lecithin contents (about 70% palmitoyl residue), the lipid of the band of Fraction T and that of the high density band of Fraction S were very active ( γ =0); whereas the lipid of the band of pulmonary washing and that of the lowest density band of Fraction S were not active, γ being 18 dyne/cm and 21 dyne/cm, respectively. This wokk brings forth three major conclusions. First, under conditions which are used to isolate serum lipoproteins, no lipoprotein was obtained from either of the three surfactant fractions and most of the lipid was found virtually free of protein. Second, the isopicnic equilibrium of a given ultracentrifugation fraction varied with the molecular structure of its constituents and could not be accounted for by the latter's average densities; instead, major roles must be player by particle geometry and their water contents. Third, although the various lipid samples contained the same quantities of palmitoyl residues (70%), the surface activities varied with the physical state of the lipid, method of assay, and some other undefined factors. [ABSTRACT FROM AUTHOR] |
Full text from SpringerLink