Key result
Theophylline reduces potassium uptake and boosts automaticity in Purkinje fibers, counteracted by norepinephrine and calcium.
Why the study?
The effect of theophylline on potassium uptake in cardiac Purkinje fibers under different conditions was not fully understood.
Does theophylline affect potassium uptake and automaticity in cardiac Purkinje fibers?
Does theophylline affect potassium uptake and automaticity in cardiac Purkinje fibers?
Theophylline decreases potassium uptake and enhances automaticity in cardiac Purkinje fibers, likely by releasing intracellular calcium and inhibiting the sodium-potassium pump.
May prompt caution with theophylline in arrhythmia-prone patients; leaves open clinical relevance of Purkinje effects.
The effect of theophylline on potassium uptake of cardiac Purkinje fibers was studied under different conditions. The following results were obtained: (1) theophylline decreases K uptake and enhances Purkinje fiber automaticity; (2) norepinephrine and high [Ca]0 counteract the decrease in K uptake induced by theophylline; (3) adrenergic receptor blockers do not modify the effect of theophylline on K uptake; (4) norepinephrine increases K uptake and this effect is potentiated by theophylline and is little affected by imidazole and acetylcholine. It is concluded that theophylline may depress K uptake by releasing intracellular calcium and thereby inhibiting the sodium-potassium pump. However, theophylline potentiates the effect of norepinephrine on K uptake probably by enhancing the intracellular levels of cyclic AMP.
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Musso et al. (2008) studied this question. Theophylline was evaluated on Potassium uptake and Purkinje fiber automaticity. Theophylline decreases potassium uptake and enhances automaticity in cardiac Purkinje fibers, an effect counteracted by norepinephrine and high extracellular calcium.
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