The alveolar type II epithelial cell: a multifunctional pneumocyte.
Castranova-V; Rabovsky-J; Tucker-JH; Miles-PR
Toxicol Appl Pharmacol 1988 May; 93(3):472-483
Methods for obtaining purified preparations of alveolar type-II cells were described, and data on the properties and functions of type-II cells were reviewed. Four methods for isolation and purification of type-II cells were discussed: density gradient centrifugation yielding 0.6 million cells per rat with a purity of 90 percent; density gradient centrifugation at a lower purity (80 percent) and higher yield (28 million cells per rat) followed by purification by differential adherence resulting in preparations of 92 percent purity and a seeding efficiency of 68 percent; centrifugal elutriation yielding 10 million cells per rat with 85 percent purity; and unit gravity sedimentation giving 90 percent type-II cells, 9 million per rat. Four functions of type-II cells were reviewed: synthesis and secretion of surfactant critical to normal lung function, with the major function of decreasing the surface tension at the air to liquid interface of the lung; a site for metabolism of foreign substances (xenobiotics), including drugs and environmental pollutants; a major mechanism of the cytochrome-P- 450 dependent monooxygenase system, which catalyzed the monooxygenation of a wide variety of lipophilic substances, and which was localized in the microsomal fraction of type-II cells and also bronchiolar nonciliated Clara cells; and the important role of type-II cells in transepithelial water movement, which was necessary to maintain the alveoli in a dry condition that minimized the distance between the alveolar air space and the pulmonary capillary blood. Type-II cells responded to exposure to high oxygen (7782447) concentrations with increased mitotic activity, with probable dedifferentiation to type-I cells, thus enhancing the lung's ability to recover from oxygen overexposure. The authors conclude that type- II cellular preparations afford bioassay systems to monitor the effects of occupational or environmental pollutants on alveolar pneumocytes and should yield important information on the etiology of pulmonary disease.
NIOSH-Author; Lung-cells; Pulmonary-system-disorders; Laboratory-animals; Alveolar-cells; Laboratory-techniques; In-vitro-studies; Environmental-pollution; Respiratory-irritants; Lung-tissue; Bioassays; Surface-properties; Microsomal-enzymes; Cell-function
Toxicology and Applied Pharmacology