Analysis of Labeling and Clearance of Lung Surfactant Phospholipids in Rabbit

Abstract

A B S T R A C T Turnover and clearance of lung surfactant phospholipids were studied with particular reference to myoinositol-induced perturbation in the acidic phospholipids. Administration of myoinositol decreased [3H]palmitate and [32P]phosphate incorporation into phosphatidylglycerol by 80-90% in whole lung, and by 94-99% in lamellar bodies and in alveolar lavage. The increased incorporation of radioactive isotopes into phosphatidylinositol following myoinositol, was inverse to the decrease in phosphatidylglycerol incorporation. Myoinositol treatment affected neither content nor labeling of phosphatidylcholine or disaturated phosphatidylcholine as studied within 50 h of administration. Phosphatidylglycerol was pulse labeled by intravenous [32P]phosphate and [3H]-palmitate, followed by myoinositol. The biological half-lives of phosphatidylglycerol in the microsomal fraction, lamellar bodies, and alveolar lavage were 1.6, 4.6, 5.4 h (with 3H), and 2.8, 6.5, 7.0 h (with 32P), respectively.32P-labeled lung surfactant tracer was applied to the airways in saline suspension and the clearance of phospholipid radioactivity was measured in alveolar lavage, alveolar macrophages, lamellar bodies and lung homogenates. The clearance rates of phosphatidylcholine, disaturated phosphatidylcholine, phosphatidylglycerol, and phosphatidylinositol as studied in whole lung over 6 h were 3.4-5.8% h. Only a small amount of phospholipid radioactivity was recovered in the alveolar macrophage fraction (including bis-[monoacylglycerol]phosphate). Phospholipid radioactivity in alveolar lavage fell to 40-70% of the maximum during the 1st h, and to 5-18% over the next

Clearance of Natural Surfactant Phosphatidylcholine from 3-Day-Old Rabbit Lungs: Effects of Dose and Species

“…Hallman et al (20) reported that radiolabeled natural surfactant was cleared from the airways and alveoli of adult rabbits to lung tissue, and the labeled phospholipids became in part associated with lamellar bodies. These observations suggested that alveolar surfactant might be recycled back into type I1 cells for reprocessing and resecretion.…”

Distribution of Endotracheally Instilled Surfactant Protein SP-C in Lung-Lavaged Rabbits

“…Uptake of surfactant phospholipids by alveolar cells was demonstrated for endotracheally administered tracer amounts of surfactant (4,(28)(29)(30)(31) and recently for treatment doses of surfactant (8,32). Bartussio et al (33) demonstrated in 3-d-old rabbits that SP-C is taken up by the lung tissue similarly to phospholipids (33).…”

Impaired recycling of surfactant-like liposomes in type II pneumocytes from injured lungs

“…This mixture was supplemented with 3 H-DPPC (specific activity 87 µCi/mg) to a final radioactivity of 1.46 nCi/µg lipid. After evaporation of the chloroform, 1 ml 0.2 M phosphate buffered saline (PBS, pH 7.4) was added and the mixture was incubated at 50°C for 15 minutes.…”

“…For resecretion experiments liposomes were prepared as described above with the following composition: 5.4 mg DPPC, 1 mg PG, 2.5 mg egg yolk PC, 1 mg cholesterol, and 0.1 mg cholesterol oleate in chloroform. 15 This mixture was supplemented with 3 H-DPPC (specific activity 87 µCi/mg) to a final radioactivity of 1.46 nCi/µg lipid and with 14 C-cholesterol oleate (specific activity 115 mCi/mg) to a final radioactivity of 1 nCi/µg lipid. The mixture was stored at 4°C and used within 1 week.…”

“…Methods: Different stages of lung injury were induced by exposing rats to 10 ppm nitrogen dioxide (NO 2 ) for 3, 20, and 28 days. Type II cells were isolated from these lungs and recycling of 3 H-DPPC labelled surfactant-like liposomes was studied in vitro. Results: Uptake of liposomes (150 µg/ml) for 20 minutes in the absence and presence of surfactant protein-A (SP-A, 5 µg/ml) was higher in cells from NO 2 injured lungs (63-78%) than in control cells.…”