Biological and Pharmaceutical Bulletin
Online ISSN : 1347-5215
Print ISSN : 0918-6158
ISSN-L : 0918-6158
Regular Article
Difference in Contractile Mechanisms between the Early and Sustained Components of Ionomycin-Induced Contraction in Rat Caudal Arterial Smooth Muscle
Kazuki Aida Mitsuo MitaReiko Ishii-Nozawa
Author information
JOURNAL OPEN ACCESS FULL-TEXT HTML
Supplementary material

2024 Volume 47 Issue 7 Pages 1368-1375

Details
Abstract

We previously reported that the sustained component of contraction induced by depolarizing stimulation by high K+ concentration in rat caudal arterial smooth muscle involves a Ca2+-induced Ca2+ sensitization mechanism whereby Ca2+ entry through voltage-gated Ca2+ channels activates proline-rich tyrosine kinase 2 (Pyk2), leading to activation of RhoA/Rho-associated kinase (ROCK). In the present study, we investigated a potential role for Pyk2-mediated RhoA/ROCK activation in contraction mediated by elevation of cytosolic free Ca2+ concentration ([Ca2+]i) induced by a Ca2+ ionophore, ionomycin, rather than by depolarizing stimulation. Ionomycin (60 µM) induced slow and sustained contraction of rat caudal arterial smooth muscle due to influx of Ca2+. Pre-treatment with a myosin light chain kinase (MLCK) inhibitor, ML-9 (30 µM), inhibited both the early phase (4 min) and the sustained phase (30 min) of ionomycin-induced contraction. On the other hand, a ROCK inhibitor, HA-1077 (3 µM), and Pyk2 inhibitors, sodium salicylate (10 mM) and PF-431396 (3 µM), suppressed only the sustained phase of ionomycin-induced contraction. A calmodulin (CaM) inhibitor, W-7 (150 µM), but not W-5 (150 µM), suppressed the early phase of contraction. Early or sustained increase of ionomycin-induced 20 kDa light chain of myosin (LC20) phosphorylation was inhibited by each inhibitor in a manner similar to the attenuation of contraction. These results indicate that the early phase of ionomycin-induced contraction is mediated by MLCK activation by [Ca2+]i elevation, whereas the sustained phase of ionomycin-induced contraction involves RhoA/ROCK activation and inhibition of myosin light chain phosphatase (MLCP) through CaM-independent Pyk2 activation by [Ca2+]i elevation.

Fullsize Image
Content from these authors
© 2024 Author(s) This is an open access article distributed under the terms of Creative Commons Attribution 4.0 License (https://creativecommons.org/licenses/by-nc/4.0/). Published by The Pharmaceutical Society of Japan

This article is licensed under a Creative Commons [Attribution-NonCommercial 4.0 International] license.
https://creativecommons.org/licenses/by-nc/4.0/
Previous article Next article
feedback
Top