Cardiac functions and taurine's actions at different extracellular calcium concentrations in forced swimming stress-loaded rats.
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.
Department of Pharmacology, Nara Medical University, Kashihara, Japan.
Hiroyasu
H
Satoh
Toshiaki
T
Nakatani
Takeshi
T
Tanaka
Satomi
S
Haga
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D003345:Corticosterone / Q000097:blood / Q000378:metabolism; D006339:Heart Rate / Q000187:drug effects*; D007150:Immunohistochemistry; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D013312:Stress, Physiological / Q000503:physiopathology*; D013550:Swimming; D013654:Taurine / Q000097:blood / Q000378:metabolism / Q000494:pharmacology*
D013654:Taurine; D002118:Calcium; D003345:Corticosterone