Surfactant apoprotein A secretion by human tracheobronchial epithelial cells.
To determine whether surfactant apoproteins are produced locally by the airway walls, we used a two-site simultaneous immunoassay with monoclonal antibodies and measured the surfactant apoprotein-A (SP-A) content in media cultured with human airway explants or cultured epithelial cells. Tracheobronchial explants were cultured for 2 successive periods (periods I and II). Significant SP-A concentrations were detected in both periods. Methacholine (MCh) or isoproterenol (ISP), added to the medium at the beginning of period II, reduced the ratio of SP-A concentration in period II to that in period I, compared to samples without treatment. The SP-A concentration in the medium at the confluent period of cultured epithelial cells was significantly higher than at the mid-period, indicating that SP-A secretion is dependent on the cell number. The supernatant from explants stimulated by MCh was capable of reducing SP-A secretion from cultured epithelial cells. Immunohistochemical study of SP-A using monoclonal antibody demonstrated positive immunoperoxidase staining in the cytoplasm of epithelial cells. Further, Western blots of electrophoresed proteins from epithelial cells showed the characteristic properties of SP-A. These findings indicate that tracheobronchial epithelium can secrete SP-A.
Masuda
T
T
First Department of Internal Medicine, Tohoku University School of Medicine, Sendai, Japan.
Andoh
Y
Y
Shimura
S
S
Ohkawara
Y
Y
Hosoda
K
K
Hashimoto
S
S
Sasaki
H
H
Takishima
T
T
D001054:Apolipoproteins A / Q000235:genetics*; D015153:Blotting, Western; D001980:Bronchi / Q000166:cytology / Q000378:metabolism*; D002478:Cells, Cultured; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D014132:Trachea / Q000166:cytology / Q000378:metabolism*
D001054:Apolipoproteins A