Why the study?
Do the Ca2+ sensitizers EMD 53998 and EMD 57033 increase sinus rate and contractile force in isolated dog heart preparations?
Do the Ca2+ sensitizers EMD 53998 and EMD 57033 increase sinus rate and contractile force in isolated dog heart preparations?
Pure Ca2+ sensitization by EMD 57033 increases myocardial contractile force without directly affecting pacemaker currents or sinus rate.
Pure Ca2+ sensitization may boost contractility without raising sinus rate in isolated preparations; leaves open clinical translation from this animal model.
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 EMD 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.
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Lakhe et al. (1998) studied this question.
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