| pA2 online © Copyright 2004 The British Pharmacological Society |
158P
GKT, University of London Winter Meeting December 2003 |
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A role for
rho-kinase in cooling-induced contraction of the rat fundus |
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Print abstractThe stomach is exposed to cold temperatures during the process of ingestion of cold food. The duration of exposure depends on the nature of the food item, solid or liquid. Cooling has been shown to induce contractions of several smooth muscles, including the rat fundus, in vitro. However, the mechanism involved in the contraction is not yet known. In this study, we examined the role of Rho-kinase activation in cooling-induced contraction of the gastric fundic strip.
Adult male Sprague-Dawley rats were used in this study. Circular muscle strips were prepared and set up for isometric tension recording in 25 ml organ baths containing Krebs' solution (gassed with 95% O2/5% CO2) at 37oC. Tissue expression of RhoA and Rho kinase was examined using RT-PCR. Differences between mean values were tested for significance using students t-test. The difference was assumed to be significant when p<0.05.
Cooling produced reproducible temperature-dependent contractions of the fundic strip, contractions being inversely proportional to the temperature (table 1). Maximum contraction was attained at 15oC. A submaximal temperature of 20oC was used in subsequent experiments. Contractile response induced by cooling was significantly attenuated in a Ca2+-free (1mM EGTA) medium. The contractile response was inhibited by 65.6±2.4% (n = 5; p<0.05).
Y-27632 (10-5M), a selective Rho-kinase inhibitor (Ishizaki et al, 2000), also significantly inhibited cooling-induced contraction, reducing the response by 80.7±6.5% (n = 7; p<0.05). Using RT-PCR it was observed that the mRNAs for RhoA and Rho-kinase were expressed in the rat fundus.
Table 1. Cooling-induced contraction of the rat fundic strip.
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Temperature
(°C)
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Contraction
(mg/mg tissue wt)
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30
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10.2±2.7
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25
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13.7±2.5
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20
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17.0±2.6
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15
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18.6±2.7
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10
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16.5±3.3
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5
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13.4±4.0
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It was concluded that cooling-induced contraction of the rat fundic strip was predominantly dependent on extracellular Ca2+ and involved the RhoA/Rho-kinase pathway.
Ishizaki T., Uehata M., Tamechika I., Keel J., Nonomura K., Maekawa M., Narumiya S. (2000). Pharmacological properties of Y-27632, a specific inhibitor of Rho-associated kinases. Mol. Pharmacol. 57, 976-983.
Funding Agency: Kuwait University Research Administration Grant No. MR 03/02.