Single and combined myocardial pharmacodynamics of xamoterol, isoprenaline and g-strophanthin in the isolated rabbit heart

European Journal of Pharmacology
E Vigholt Sørensen, F Nielsen-Kudsk

Abstract

The myocardial effects of g-strophanthin and the partial beta 1-adrenoceptor agonist xamoterol were compared to the effects of isoprenaline in the isolated spontaneously beating rabbit heart. Xamoterol and g-strophanthin both produced a distinct maximum increase in contractility as shown by the increase in isotonic contraction rate from 100 to 142% (pD2 7.51) and 151% (pD2 6.54), respectively, which was however less pronounced than the increase to 200% (pD2 7.81) caused by isoprenaline. The maximum chronotropic effect of xamoterol was moderate with a frequency increase from 100 to 128% (pD2 7.40) as was the increase in oxygen consumption to 130% (pD2 7.16), and no arrhythmias were seen. The positive inotropic range of g-strophanthin was very narrow (about 60-600 nM) and cardiac toxicity just overlapped and rapidly increased over this range. Xamoterol at a fixed concentration of 28 nM caused a rightwards shift of the isoprenaline concentration-response curves demonstrating the competitive beta 1-adrenoceptor blocking effect of the drug. G-strophanthin at a concentration of 268 nM acted additively with xamoterol with regard to maximum contractility and without causing any further increase in myocardial oxygen consumption except a...Continue Reading

References

Nov 1, 1979·Journal of Cardiovascular Pharmacology·F BusseT Peters
May 1, 1985·British Journal of Pharmacology·E MaltaC Raper
Mar 1, 1968·British Journal of Pharmacology and Chemotherapy·K KuschinskyP A van Zwieten
Oct 1, 1982·British Journal of Pharmacology·A Nuttall, H M Snow

❮ Previous
Next ❯

Related Concepts

Related Feeds

Arrhythmia

Arrhythmias are abnormalities in heart rhythms, which can be either too fast or too slow. They can result from abnormalities of the initiation of an impulse or impulse conduction or a combination of both. Here is the latest research on arrhythmias.

Atrial Fibrillation

Atrial fibrillation is a common arrhythmia that is associated with substantial morbidity and mortality, particularly due to stroke and thromboembolism. Here is the latest research.