Ascorbate uptake by isolated rat alveolar macrophages and type II cells.
Castranova-V; Wright-JR; Colby-HD; Miles-PR
J Appl Physiol: Respir Environ Exercise Physiol 1983 Jan; 54(1):208-214
Measurements were made of the intracellular ascorbate concentrations (IACs) in three fractions of isolated pneumocytes from male Sprague- Dawley-rats, specifically alveolar macrophages, type II cells, and other lung cells; and studies were carried out to determine the characteristics of ascorbate uptake in these fractions. IACs were measured by incubating the cells in media containing 0.1 millimolar (mM) ascorbate and spectrophotometrically comparing the optical densities of samples against standards. IACs were 3.2mM in alveolar macrophages and type II cells and 0.9mM in other lung cells. Ascorbate uptake was measured by means of labeled ascorbic-acid and a liquid scintillation spectrometer. The time course of ascorbate uptake in each cell type exhibited an initial minor component that was rapid and lasted less than 15 minutes, and a major component that was linear from 15 to 120 minutes. The rates of uptake during the major component decreased in the order alveolar macrophages, type II cells, and other cells. In alveolar microphages and type II cells, ascorbate influx followed saturation kinetics and was dependent on extracellular sodium and metabolic inhibitors. The authors suggest that high dietary levels of ascorbate may be useful in protecting the lung from oxidant injury.
NIOSH-Author; Antioxidation; Pulmonary-system; Kinetics; Oxidizers; Diet; Transport-mechanisms; Prophylaxis;
Author Keywords: ascorbate transport; pneumocytes
Journal of Applied Physiology: Respiratory, Environmental and Exercise Physiology