Cardiac functions and taurine's actions at different extracellular calcium concentrations in forced swimming stress-loaded rats |
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Authors: | Satoh Hiroyasu Nakatani Toshiaki Tanaka Takeshi Haga Satomi |
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Institution: | (1) Department of Pharmacology, Division of Cellular and Molecular Biology, Nara Medical University, Kashihara, 634 Nara, Japan |
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Abstract: | Modulation of the sinus rate and contractile force by taurine at different extracellular Ca2+ concentrations (Ca2+]o) was examined using rat right atria loaded with forced swimming stress. Serum concentration of corticosterone profoundly
increased in stress-loaded rats as compared with native rats. The taurine level in serum also increased in stress-loaded rats,
but was not changed in the different heart tissues and aorta. Heat-shock protein (HSP72) was detectable in cardiac muscles
and in the lumen of cardiac blood vessels of stress-loaded rats using a monoclonal antibody. Increasing Ca2+]o (from 0.9 to 3.6 mM) enhanced the sinus rate and contractile force in a Ca2+]o-dependent fashion in native rats, but not in stress-loaded rats. Taurine (1–20 mM) caused a negative chronotropic and inotropic effect in a concentration-dependent manner. At 1.8 mM Ca2+]o, the negative chronotropic effect of taurine (10–20 mM) was attenuated in stress-loaded rats as compared with native rats. These results indicate that swimming stress causes a
release of taurine into the serum and reduces the sensitivity to Ca2+]o. Taurine administration might, in part, exhibit the protective actions on acute stress-induced responses. |
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Keywords: | Forced swimming stress HSP corticosterone subsensitivity taurine taurine concentration contractile force sinus rate rat heart |
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