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Alveolar type II cell cNOS activity and ATP levels are increased by lung surfactant or DPPC vesicles.

Authors
Miles-PR; Bowman-L; Rengasamy-A; Huffman-L
Source
Am J Physiol, Lung Cell Mol Physiol 1997 Aug; 273(2):L339-L346
NIOSHTIC No.
20033931
Abstract
In a previous study, we reported that nitric oxide (.NO) affects surfactant synthesis and ATP levels in alveolar type II cells and suggested that there is constitutive nitric oxide synthase (cNOS) activity in the cells. In the present study, we performed experiments to confirm further the presence of cNOS and to determine the effects of lung surfactant on type II cell .NO and ATP levels. The supernatant from freshly isolated cells contains .NO (0.26 +/- 0.08 nmol/10(6) cells). During incubation, the cells produce additional .NO at a rate of approximately 0.3 nmol.10(5) cells-1.h-1. .NO formation is inhibited by 28-46% by three inhibitors of cNOS and inducible NOS (iNOS), NG-monomethyl-L-arginine (L-NMMA), L-N5-(1-iminoethyl)ornithine hydrochloride, and NG-nitro-L-arginine methyl ester, but a specific inhibitor of iNOS, aminoguanidine, has no effect. The production of .NO is reduced in Ca(2+)-free medium, is stimulated by the Ca2+ ionophore A-23187, and is independent of extracellular L-arginine. One known type of cNOS, endothelial NOS (eNOS), can be detected in the cells by using Western blot analysis. Incubation of the cells with lung surfactant leads to a relatively rapid (approximately 15 min), concentration-dependent increase in .NO formation that reaches levels as high as 238 +/- 14% of control. The surfactant effects appear to be caused by its major component, dipalmitoyl phosphatidylcholine (DPPC). Exposure of type II cells to DPPC results in maximal increases in .NO formation, ATP content, and O2 consumption, which are 268 +/- 32, 234 +/- 24, and 131 +/- 6% of control, respectively. The DPPC-induced increases in .NO, ATP, and O2 consumption are inhibited by L-NMMA. These results confirm the presence of type II cell cNOS and suggest that it may have a role in the cellular processing of lung surfactant.
Keywords
Lung-cells; Lung-irritants; Alveolar-cells; Cell-function; Cellular-function; Cellular-reactions
CODEN
APLPE7
CAS No.
10102-43-9
Publication Date
19970801
Document Type
Journal Article
Fiscal Year
1997
NTIS Accession No.
NTIS Price
Issue of Publication
2
ISSN
1040-0605
NIOSH Division
HELD
Source Name
American Journal of Physiology: Lung Cellular and Molecular Physiology
State
WV
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