Why the study?
Does theophylline affect phasic tension and slow inward current in isolated frog atrial fibres?
Does theophylline affect phasic tension and slow inward current in isolated frog atrial fibres?
Theophylline increases phasic tension and slow inward current in frog atrial fibres, likely via phosphodiesterase inhibition, and potentiates isoprenaline effects dependent on endogenous catecholamines.
No clinical implications for human cardiac therapy; leaves open PDE-mediated effects on Isi in isolated amphibian models.
The action of theophylline on phasic tension and slow inward current (Isi) was investigated on isolated voltaged-clamped frog atrial fibres. The action of theophylline was both dose- and time-dependent; the most effective dose was 2.10(-3)M. Theophylline induced a rapid positive inotropic effect which cannot be attributed to a beta-adrenoceptor stimulation or to an adenosine antagonism; this effect was closely related to an increase in slow inward current (Isi), probably due to an inhibition of phosphodiesterase activity and a subsequent increase in cAMP content. The decline of the positive inotropic effect of theophylline was discussed in terms of additional effects of the drug. Theophylline, consistently with its phosphodiesterase inhibitory action, was shown to potentiate the effects of isoprenaline on phasic tension and Isi; however no potentiation was observed after reserpine-induced depletion of endogenous catecholamines. It might be thought that non-specific effects of reserpine on some steps of cardiac excitation-contraction coupling counteract the effects of theophylline.
No takes yet. Share an insight, caveat, or question.
Gauthier et al. (1991) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: