These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Inhibition of myocardial Na(+)-K(+)-ATPase activity by bretylium: role of potassium.
    Author: Dzimiri N, Almotrefi AA.
    Journal: Arch Int Pharmacodyn Ther; 1992; 318():76-85. PubMed ID: 1334399.
    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.
    [Abstract] [Full Text] [Related] [New Search]