Effect of surfactant protein A on granular pneumocyte surfactant secretion in vitro.
Surfactant secretion by lung type II cells occurs when lamellar bodies (LBs) fuse with the plasma membrane and surfactant is released into the alveolar lumen. Surfactant protein A (SP-A) blocks secretagogue-stimulated phospholipid (PL) release, even in the presence of surfactant-like lipid. The mechanism of action is not clear. We have shown previously that an antibody to LB membranes (MAb 3C9) can be used to measure LB membrane trafficking. Although the ATP-stimulated secretion of PL was blocked by SP-A, the cell association of iodinated MAb 3C9 was not altered, indicating no effect on LB movement. FM1-43 is a hydrophobic dye used to monitor the formation of fusion pores. After secretagogue exposure, the threefold enhancement of the number of FM1-43 fluorescent LBs (per 100 cells) was not altered by the presence of SP-A. Finally, there was no evidence of a large PL pool retained on the cell surface through interaction with SP-A. Thus SP-A exposure does not affect these stages in the surfactant secretory pathway of type II cells.
Bates
Sandra R
SR
Institute for Environmental Medicine, University of Pennsylvania, School of Medicine, Philadelphia, Pennsylvania 19104-6068, USA. batekenn@mail.med.upenn.edu
Tao
Jian-Qin
JQ
Notarfrancesco
Kathleen
K
DeBolt
Kristine
K
Shuman
Henry
H
Fisher
Aron B
AB
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001688:Biological Products / Q000494:pharmacology; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D002462:Cell Membrane / Q000502:physiology; D002478:Cells, Cultured; D007700:Kinetics; D008081:Liposomes / Q000494:pharmacology; D008168:Lung / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010743:Phospholipids / Q000378:metabolism / Q000494:pharmacology; D011650:Pulmonary Alveoli / Q000187:drug effects / Q000502:physiology; D037662:Pulmonary Surfactant-Associated Protein A / Q000378:metabolism* / Q000494:pharmacology*; D037661:Pulmonary Surfactant-Associated Proteins / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D001688:Biological Products; D008081:Liposomes; D010743:Phospholipids; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D000255:Adenosine Triphosphate; C072197:beractant