Inhibition of myocardial Na(+)-K(+)-ATPase activity by bretylium: role of potassium.

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Dzimiri N, Almotrefi AA

Inhibition of myocardial Na(+)-K(+)-ATPase activity by bretylium: role of potassium.

Arch Int Pharmacodyn Ther. 1992 Jul-Aug;318:76-85.

PubMed ID

1334399 [ View in PubMed

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Abstract

The effects of bretylium on the Mg(2+)-dependent ATP-hydrolytic action of myocardial Na(+)-K(+)-ATPase (EC 3.6.1.3) were studied in guinea-pig heart preparations in media containing various K+ concentrations. Under "standard" conditions (5 mM K+), bretylium inhibited the Na(+)-K(+)-ATPase activity in a concentration-dependent fashion in the range of 0.001-80 mM, with an IC20 value of 0.19 +/- 0.05 mM and an IC50 value of 1.38 +/- 0.11 mM. Reducing the K+ concentration from 5 to 2.5 mM enhanced the inhibitory action, shifting the effective (5-95% inhibition) concentration range to 0.0003-9.6 mM, with IC20 and IC50 values of 0.036 +/- 0.004 mM and 0.92 +/- 0.30 mM, respectively. On the other hand, increasing the K+ concentration to 10 mM shifted the range to 10-90 mM. The corresponding IC20 value was 0.48 +/- 0.02 mM and the IC50 was 2.24 +/- 0.36 mM. The results show that K+ plays an important role in the inhibition of myocardial Na(+)-K(+)-ATPase activity by bretylium. This is probably pertinent to the mode by which the drug may interfere with the electrogenic Na+/K+ pump activity of the enzyme, and, consequently, cause or aggravate cardiac arrhythmias.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Bretylium	Sodium/potassium-transporting ATPase subunit alpha-1	Protein	Humans	Yes	Inhibitor	Details