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Mediators of Inflammation
Volume 2007, Article ID 24174, 6 pages
http://dx.doi.org/10.1155/2007/24174
Research Article

Resting Tension Affects eNOS Activity in a Calcium-Dependent Way in Airways

1Department of Physiology, Medical School, University of Thessaly, Papakiriazi 22, Larissa 41222, Greece
2Department of Respiratory Medicine, Medical School, University of Thessaly, Papakiriazi 22, Larissa 41222, Greece

Received 14 December 2006; Accepted 5 February 2007

Copyright © 2007 Eudoxia Kitsiopoulou et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The alteration of resting tension (RT) from 0.5 g to 2.5 g increased significantly airway smooth muscle contractions induced by acetylcholine (ACh) in rabbit trachea. The decrease in extracellular calcium concentration [Ca2+]o from 2 mM to 0.2 mM reduced ACh-induced contractions only at 2.5 g RT with no effect at 0.5 g RT. The nonselective inhibitor of nitric oxide synthase (NOS), NG-nitro-L-arginine methyl ester (L-NAME) increased ACh-induced contractions at 2.5 g RT. The inhibitor of inducible NOS, S-methylsothiourea or neuronal NOS, 7-nitroindazole had no effect. At 2.5 g RT, the reduction of [Ca2+]o from 2 mM to 0.2 mM abolished the effect of L-NAME on ACh-induced contractions. The NO precursor L-arginine or the tyrosine kinase inhibitors erbstatin A and genistein had no effect on ACh-induced contractions obtained at 2.5 g RT. Our results suggest that in airways, RT affects ACh-induced contractions by modulating the activity of epithelial NOS in a calcium-dependent, tyrosine-phosphorylation-independent way.