Affordable Access

deepdyve-link
Publisher Website

Pressure-dependent contribution of Rho kinase-mediated calcium sensitization in serotonin-evoked vasoconstriction of rat cerebral arteries.

Authors
  • El-Yazbi, Ahmed F1
  • Johnson, Rosalyn P
  • Walsh, Emma J
  • Takeya, Kosuke
  • Walsh, Michael P
  • Cole, William C
  • 1 The Smooth Muscle Research Group, Department of Physiology and Pharmacology, Faculty of Medicine, University of Calgary, 3330 Hospital Drive N.W., Calgary, Alberta, Canada T2N 4N1. , (Canada)
Type
Published Article
Journal
The Journal of Physiology
Publisher
Wiley (Blackwell Publishing)
Publication Date
May 15, 2010
Volume
588
Issue
Pt 10
Pages
1747–1762
Identifiers
DOI: 10.1113/jphysiol.2010.187146
PMID: 20351047
Source
Medline
License
Unknown

Abstract

Our understanding of the cellular signalling mechanisms contributing to agonist-induced constriction is almost exclusively based on the study of conduit arteries. Resistance arteries/arterioles have received less attention as standard biochemical approaches lack the necessary sensitivity to permit quantification of phosphoprotein levels in these small vessels. Here, we have employed a novel, highly sensitive Western blotting method to assess: (1) the contribution of Ca(2+) sensitization mediated by phosphorylation of myosin light chain phosphatase targeting subunit 1 (MYPT1) and the 17 kDa PKC-potentiated protein phosphatase 1 inhibitor protein (CPI-17) to serotonin (5-HT)-induced constriction of rat middle cerebral arteries, and (2) whether there is any interplay between pressure-induced myogenic and agonist-induced mechanisms of vasoconstriction. Arterial diameter and levels of MYPT1 (T697 and T855), CPI-17 and 20 kDa myosin light chain subunit (LC(20)) phosphorylation were determined following treatment with 5-HT (1 micromol l(1)) at 10 or 60 mmHg in the absence and presence of H1152 or GF109203X to suppress the activity of Rho-associated kinase (ROK) and protein kinase C (PKC), respectively. Although H1152 and GF109203X suppressed 5-HT-induced constriction and reduced phospho-LC(20) content at 10 mmHg, we failed to detect any increase in MYPT1 or CPI-17 phosphorylation. In contrast, an increase in MYPT1-T697 and MYPT1-T855 phosphorylation, but not phospho-CPI-17 content, was apparent at 60 mmHg following exposure to 5-HT, and the phosphorylation of both MYPT1 sites was sensitive to H1152 inhibition of ROK. The involvement of MYPT1 phosphorylation in the response to 5-HT at 60 mmHg was not dependent on force generation per se, as inhibition of cross-bridge cycling with blebbistatin (10 micromol l(1)) did not affect phosphoprotein content. Taken together, the data indicate that Ca(2+) sensitization owing to ROK-mediated phosphorylation of MYPT1 contributes to 5-HT-evoked vasoconstriction only in the presence of pressure-induced myogenic activation. These findings provide novel evidence of an interplay between myogenic- and agonist-induced vasoconstriction in cerebral resistance arteries.

Report this publication

Statistics

Seen <100 times