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Enhanced sensitivity to digoxin in dystrophic mice
Abstract:
We estimated the effect of digoxin on the myocardial potassium content and the action potentials of the left ventricular papillary muscles in dystrophic mice (C57BL/6JCL dy X dy). All of 10 dystrophic mice died following ip injection of digoxin at a dose of one quarter of the iv LD50 for normal mice. The myocardial digoxin concentration and the myocardial potassium content in dystrophic mice were similar to those in normal mice before and 60 min after the ip injection of digoxin. The action potential durations (APD) in dystrophic mice were significantly longer than those in normal mice. Perfusion of digoxin (2 micrograms/ml) for 30 min reduced the APD significantly and induced arrhythmias in dystrophic mice, but it did not bring about any significant change in normal mice. These data suggest that dystrophic mice have increased sensitivity to digitalis. This hypersensitivity to digitalis is not due to increased myocardial digoxin uptake or decreased myocardial potassium content.
Insights
Dystrophic mice exhibit heightened sensitivity to digoxin, a heart medication. This increased sensitivity is not linked to altered digoxin levels or potassium in heart muscle, but rather to longer action potential durations.
Area of Science:
- Cardiology
- Pharmacology
- Genetics
Background:
- Digoxin is a cardiac glycoside used to treat heart conditions.
- Duchenne muscular dystrophy (DMD) is a genetic disorder affecting muscle function.
- The cardiac effects of digoxin in dystrophic models require further investigation.
Purpose of the Study:
- To investigate the impact of digoxin on myocardial potassium content and cardiac action potentials in dystrophic mice.
- To determine the underlying mechanisms of potential digoxin hypersensitivity in this model.
Main Methods:
- Intraperitoneal injection and ex vivo perfusion of digoxin in dystrophic (dy/dy) and normal mice.
- Measurement of myocardial digoxin and potassium concentrations.
- Electrophysiological recordings of left ventricular papillary muscle action potentials.
Main Results:
- Dystrophic mice showed significantly longer action potential durations (APD) compared to normal mice.
- Intraperitoneal digoxin injection was lethal to all dystrophic mice at a sub-lethal dose for normal mice.
- Digoxin perfusion shortened APD and induced arrhythmias in dystrophic mice, but not in normal mice.
- Myocardial digoxin and potassium levels were similar between dystrophic and normal mice post-injection.
Conclusions:
- Dystrophic mice display increased sensitivity to digoxin.
- This hypersensitivity is not attributable to altered myocardial digoxin uptake or potassium content.
- The prolonged APD in dystrophic mice may contribute to their heightened susceptibility to digoxin toxicity.