Surfactant apoprotein A (SP-A) is synthesized in airway cells.
The pulmonary surfactant apoproteins A, B, and C (SP-A, SP-B, and SP-C, respectively) function in concert with surfactant phospholipids to reduce surface pressure in the alveolus. Surfactant apoproteins also regulate surfactant synthesis, secretion, adsorption, and recycling. SP-A and B have been localized by immunocytochemistry to alveolar epithelial (type II) cells, alveolar macrophages, and nonciliated bronchiolar epithelial (Clara) cells. In contrast, in situ hybridization to SP-A and B mRNA in human lung has shown SP-A and B transcripts in type II cells, but only SP-B message in Clara cells, implying that synthesis of SP-A occurs exclusively in type II cells. In this report, in situ hybridization to SP-A mRNA was performed on adult and developing rabbit lung and on human lung. SP-A transcripts were found in type II cells and bronchiolar epithelium of both species. The distribution of SP-A message-containing cells in the bronchiolar epithelium of rabbits and humans was similar to the distribution of Clara cells in these two species. These data indicate that SP-A is not only synthesized in type II cells but also in Clara cells.
Auten
R L
RL
Department of Pediatrics (Neonatology), University of Rochester Medical Center, New York 14642.
Watkins
R H
RH
Shapiro
D L
DL
Horowitz
S
S
D000818:Animals; D001059:Apoproteins / Q000096:biosynthesis*; D001980:Bronchi / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism; D005865:Gestational Age; D006801:Humans; D008168:Lung / Q000196:embryology / Q000378:metabolism*; D009693:Nucleic Acid Hybridization; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000096:biosynthesis*; D015347:RNA Probes; D012333:RNA, Messenger / Q000032:analysis; D011817:Rabbits
D001059:Apoproteins; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; D015347:RNA Probes; D012333:RNA, Messenger; C046616:pulmonary surfactant apoprotein