Role of nitric oxide and superoxide anion in spontaneous lung chemiluminescence. Barnard, Michele L., Blair Robertson, Benjamin P. Watts, Jr., and Julio F. Turrens. Michael Reese Hospital and Medical Center, Department of Pulmonary and Critical Care Medicine, Chicago, IL 60616 and Department of Biomedical Sciences, University of South Alabama, Mobile, AL 36688
APStracts 3:0175L, 1996.
Inhibition of x NO synthase by nitro-L-arginine (NLA) decreased baseline chemiluminescence in a dose-dependent fashion up to 78% at 300 [mu]M NLA. This inhibition was prevented by pretreatment with 1 mM arginine. Similarly, addition of superoxide dismutase (200 U/ml) to the perfusion buffer inhibited spontaneous light emission by 57%. Addition of NLA after SOD or vice versa did not inhibit light emission any further, suggesting that both x NO and O were precursors of the same oxidant. Production of additional extracellular O by neutrophils activated with phorbol myristate acetate increased light emission by more than 200 percent, but this increase was insensitive to NLA. Increasing the intracellular steady state O concentration by perfusion of control lungs with the Cu,Zn superoxide dismutase inhibitor diethyldithio-carbamate (DDC, 1 mM), stimulated light emission up to 4-fold, but this spontaneous chemiluminescence was also insensitive to NLA. In experiments using cultured endothelial cells supplemented with extracellular bovine serum albumin (BSA), 5 [mu]M of the Ca2+-ionophore A23187 (a stimulant of x NO synthase) stimulated chemiluminescence of by 40%. This increase was again SOD- and NLA-sensitive. Addition of NLA after SOD or vice versa did not change light emission. These results suggest that the background chemiluminescence of isolated perfused intact lungs may result from the constant release of small amounts of O and x NO by endothelial cells into the capillary lumen, which in turn reacts with BSA in the perfusion buffer. 

Received 6 July 1995; accepted in final form 1 October 1996.
APS Manuscript Number L231-5.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996