Search results for "Ca influx"

�ber den Mechanismus der positiv inotropen Wirkung von Theophyllin am Warmbl�terherzen

1971

In order to further elucidate the mechanism of the positive inotropiceffect of theophylline (T) in mammalian cardiac muscle, the influence of T on contractile force, extracellular space,45Ca uptake,45Ca release, and total myocardial calcium concentration was investigated in isolated, electrically driven (frequency 170 beats/min) or quiescent left guinea-pig atria. The investigations were performed in Tyrode solution containing 0.45 mM CaCl2. T concentration was 5×10−4 g/ml. Under these conditions, T exerted maximal positive inotropic but no toxic effects, that is, it did not cause contractures or arrythmias within 60 min (Fig. 1). The experiments provide evidence that T increases the rate o…