Jpn. J. Pharmacol. 76 (4), 435-439 (1998)

Different Chronotropic and Inotropic Effects of EMD 57033 and EMD 53998, Ca2+ Sensitizers, on Isolated, Blood-Perfused Dog Heart Preparations

Manoj Lakhe, Yasuyuki Furukawa (*), Takanori Yonezawa, Masamichi Hirose, Yoshito Nagashima, Yusuke Miyashita and Shigetoshi Chiba

Department of Pharmacology, Shinshu University School of Medicine, Matsumoto 390-8621, Japan
(*) To whom correspondence should be addressed.

Abstract: To investigate whether a Ca2+ sensitizer increases sinus rate, we studied the effects of racemic thiadiazinone, EMD 53998 (a Ca2+ sensitizer with phosphodiesterase inhibitory action) and its (+)-enantiomer BMD 57033 (a relatively pure Ca2+ sensitizer) on isolated, blood-perfused spontaneously beating right atria and paced left ventricles of the dogs. EMD 53998 increased sinus rate dose-dependently, but EMD 57033 did not. Both substances increased atrial and ventricular contractile force. Propranolol did not affect the responses to each substance. These results suggest that the Ca2+ sensitizing action induced by EMD 57033 does not affect pacemaker currents directly.

Keywords: EMD 57033, Ca2+ sensitizer, Sinus rate

Copyrightę The Japanese Pharmacological Society 1998

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