Pulmonary surfactant protein A-mediated uptake of phosphatidylcholine by alveolar type II cells.
Pulmonary surfactant protein A (SP-A)-mediated uptake of phosphatidylcholine (PC) by alveolar type II cells was investigated. SP-A enhanced the uptake of liposomes containing dipalmitoylphosphatidylcholine (DPPC), 1-palmitoyl-2-linoleoyl phosphatidylcholine (PLPC), or 1,2-dihexadecyl-sn-glycero-3-phosphocholine (DPPC-ether), a diether analogue of DPPC, but about twice as much DPPC was taken up by type II cells as PLPC or DPPC-ether. When subcellular distribution was analyzed, 51.3 +/- 2.9% (mean +/- SD, n = 3) of cell-associated radiolabeled DPPC was recovered in the lamellar body-rich fraction in the presence of SP-A, whereas only 19.3 +/- 1.9% (mean +/- SD, n = 3) was found to this fraction in the absence of SP-A. When type II cells were incubated either with DPPC at 0 degree C or with DPPC-ether at 37 degrees C, or no cells were included, low proportions of the cell-associated lipids were present in the fractions corresponding to lamellar bodies even in the presence of SP-A. Anti-SP-A antibody significantly reduced the radioactivity incorporated into the lamellar body fraction. Phosphatidylcholine that had been incorporated into lamellar bodies remained largely intact when SP-A was present. Subcellular fractionations of type II cells with radiolabeled SP-A and DPPC revealed that the sedimentation characteristics of cell-associated SP-A are different from those of DPPC, although a small broad peak of radiolabeled SP-A was found in the lamellar body fraction.(ABSTRACT TRUNCATED AT 250 WORDS)
Tsuzuki
A
A
Department of Biochemistry, Sapporo Medical College, Japan.
Kuroki
Y
Y
Akino
T
T
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000493:pharmacokinetics; D000818:Animals; D002499:Centrifugation, Density Gradient; D050356:Lipid Metabolism; D008081:Liposomes / Q000378:metabolism; D008297:Male; D010713:Phosphatidylcholines / Q000493:pharmacokinetics*; D010743:Phospholipids / Q000378:metabolism; D011510:Proteolipids / Q000494:pharmacology*; D011650:Pulmonary Alveoli / Q000166:cytology* / Q000378:metabolism*; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013347:Subcellular Fractions / Q000378:metabolism
D008081:Liposomes; D010713:Phosphatidylcholines; D010743:Phospholipids; D011510:Proteolipids; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; D015060:1,2-Dipalmitoylphosphatidylcholine