title: Degradation of dipalmitoyl phosphatidylcholine by isolated rat granular pneumocytes and reutilization for surfactant synthesis.
abstract: We investigated metabolic utilization of exogenous (modelled after lung surfactant) phospholipids by granular pneumocytes in primary culture. Cells were incubated for 21, 65, and 140 min with [3H-methyl]dipalmitoylphosphatidylcholine (DPPC) containing liposomes prepared from synthetic lipids. Radioactivity in cellular phosphatidylcholine (PC) declined steadily to 50% of the total trypsin-resistant cell-associated radioactivity. The proportion of radioactivity increased with time in cytidine-5'-diphosphate-choline and phosphorylcholine, which suggested reutilization of choline for PC synthesis. Cells incubated with liposomes for 2 h revealed that of the total cell-associated radioactivity, 7% was in lamellar bodies and 10% in the microsomal fraction. The lipid-associated radioactivity was 24% in "soluble," 96% in lamellar bodies, and 92% in the microsomal fraction. Percent of total PC label recovered in disaturated PC of microsomal fractions decreased (slope = -5.27%/h) with time of incubation (r = 0.67). Incubation of cells with liposomes containing ([3H-methyl]choline-[14C]palmitoyl) DPPC led to altered isotope ratios in both lamellar bodies and microsomes. These observations indicate that granular pneumocytes degrade exogenous PC and resynthesize PC from degradation products.
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000378:metabolism*; D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D002738:Chloroquine / Q000494:pharmacology; D002794:Choline / Q000378:metabolism; D008081:Liposomes; D008168:Lung / Q000166:cytology* / Q000378:metabolism; D008744:Methylamines / Q000494:pharmacology; D009940:Organoids / Q000378:metabolism; D011663:Pulmonary Surfactants / Q000096:biosynthesis*; D011796:Quinacrine / Q000494:pharmacology; D051381:Rats
chemical_list: D008081:Liposomes; D008744:Methylamines; D011663:Pulmonary Surfactants; D000643:Ammonium Chloride; D015060:1,2-Dipalmitoylphosphatidylcholine; D002738:Chloroquine; C027451:methylamine; D011796:Quinacrine; D002794:Choline