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Advances in Pharmacological Sciences
Volume 2008, Article ID 362741, 9 pages
http://dx.doi.org/10.1155/2008/362741
Research Article

Distinct Effects of Contraction Agonists on the Phosphorylation State of Cofilin in Pulmonary Artery Smooth Muscle

1Department of Pharmacology, Center of Biomedical Research Excellence, University of Nevada School of Medicine, Reno, NV 89557, USA
2Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA

Received 5 March 2007; Accepted 24 July 2007

Academic Editor: Charles Klodell

Copyright © 2008 Yan-Ping Dai 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

We hypothesized that agonist-induced contraction correlates with the phospho-cofilin/cofilin (P-CF/CF) ratio in pulmonary artery (PA) rings and cultured smooth muscle cells (PASMCs). PA rings were used for isometric contractions and along with PASMCs for assay of P-CF/CF by isoelectric focusing and immunoblotting. The P-CF/CF measured 22.5% in PA and differentiated PASMCs, but only 14.8% in undifferentiated PASMCs. With comparable contraction responses in PA, endothelin-1 (100 nM) and norepinephrine (1  M) induced a 2-fold increase of P-CF/CF, while angiotensin II (1  M) induced none. All agonists activated Rho-kinase and LIMK2, and activation was eliminated by inhibition of Rho-kinase. Microcystin LF (20 nM) potentiated the angiotensin II, but not the 5-hydroxytryptamine (1  M)-mediated increase of P-CF/CF. In conclusion, all tested agonists activate the Rho-kinase-LIMK pathway and increase P-CF/CF. Angiotensin II activates PP2A and counteracts the LIMK-mediated CF phosphorylation. CF phosphorylation stabilizes peripheral actin structures and may contribute to the maximal contraction of PA.