Isolated rat alveolar type II cells protrude intracellular lamellar bodies by forming bubble-like structures during surfactant secretion.
Pulmonary surfactant is synthesized and secreted by pulmonary alveolar type II epithelial cells (type II cells). It passes through the alveolar lining fluid and adsorbs to the air-liquid interface. The process from secretion to adsorption is not yet entirely understood. To acquire a detailed understanding of this process, we used multiple observations of type II cells isolated from rat lungs under electron microscopy (EM) and confocal laser scanning microscopy (CLSM). Transmission EM observation demonstrated a loosening process of the intracellular lamellar bodies from the inside to the outside of the cell. Scanning EM observation revealed bubble-like protrusions from the cell surface, and differential interference contrast microscopy illustrated the protrusions expanding with time. CLSM observation with FM 1-43, a fluorescent membrane probe, revealed that the bubble-like protrusions were composed of phospholipids. Thus, we have demonstrated that isolated rat type II cells protrude intracellular lamellar bodies by forming bubble-like structures, possibly enabling them to adsorb to the air-liquid interface directly. These observations suggest a new mechanism for surfactant secretion from type II cells.
Ogasawara
Rie
R
Department of Laboratory Medicine, School of Medicine, Iwate Medical University, 19-1 Uchimaru, Morioka, Iwate 020-8505, Japan. rogasawa@iwate-med.ac.jp
Yoshida
Yasuo
Y
Tohyama
Koujiro
K
Satoh
Yoh-ichi
Y
Suwabe
Akira
A
D000818:Animals; D002469:Cell Separation; D022081:Cell Surface Extensions / Q000378:metabolism / Q000648:ultrastructure*; D008297:Male; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D011650:Pulmonary Alveoli / Q000378:metabolism / Q000648:ultrastructure*; D011663:Pulmonary Surfactants / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020545:Respiratory Mucosa / Q000378:metabolism / Q000648:ultrastructure*
D011663:Pulmonary Surfactants