Document Detail


Ascorbate uptake by isolated rat alveolar macrophages and type II cells.
MedLine Citation:
PMID:  6826406     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Studies were conducted to measure intracellular ascorbate content and to characterize ascorbate uptake in three fractions of isolated rat pneumocytes (i.e., alveolar macrophages, alveolar type II epithelial cells, and another fraction of small pneumocytes that contains neither macrophages nor type II cells). When cells are incubated in medium containing 0.1 mM ascorbate (i.e., the concentration normally found in plasma), intracellular ascorbate concentrations are 3.2 mM in alveolar macrophages and type II cells and 0.9 mM in other lung cells; ascorbate influx is 1.5 nmol . 10(7) cells-1 . h-1 for alveolar macrophages, 0.24 nmol . 10(7) cells-1 . h-1 for type II cells, and very slow in other pneumocytes. Ascorbate influx displays saturation kinetics in both alveolar macrophages (K1/2 = 2 mM; Vmax = 32.2 nmol . 10(7) cells-1 . h-1) and type II cells (K1/2 = 5 mM; Vmax = 14.2 nmol . 10(7) cells-1 . h-1). After correction for differences in the membrane surface areas of these two types of lung cells, the rates for maximum ascorbate influx (Vmax) are similar in alveolar macrophages and type II cells. In addition, ascorbate uptake by alveolar macrophages and type II cells is dependent on metabolic activity and extracellular sodium. In contrast, ascorbate uptake in other lung cells does not exhibit saturation kinetics and is not dependent on metabolism or sodium. Thus alveolar macrophages and type II cells possess an energy-dependent cotransport system for ascorbate and sodium influx. The high ascorbate content and the existence of a specialized transport mechanism for ascorbate uptake may explain the relative resistance of alveolar macrophages and type II cells to oxidant injury.
Authors:
V Castranova; J R Wright; H D Colby; P R Miles
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of applied physiology: respiratory, environmental and exercise physiology     Volume:  54     ISSN:  0161-7567     ISO Abbreviation:  J Appl Physiol Respir Environ Exerc Physiol     Publication Date:  1983 Jan 
Date Detail:
Created Date:  1983-04-15     Completed Date:  1983-04-15     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  7801242     Medline TA:  J Appl Physiol Respir Environ Exerc Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  208-14     Citation Subset:  IM    
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MeSH Terms
Descriptor/Qualifier:
Animals
Ascorbic Acid / metabolism*
Biological Transport
Biotransformation
Lung / cytology,  metabolism*
Macrophages / metabolism*
Male
Pulmonary Alveoli / cytology,  metabolism*
Rats
Rats, Inbred Strains
Sodium / pharmacology
Time Factors
Chemical
Reg. No./Substance:
50-81-7/Ascorbic Acid; 7440-23-5/Sodium

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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