Related Experiment Videos
Sodium pump and calcium channel modulation of Mg-deficiency cardiomyopathy
1Department of Pathology, George Washington University Medical Center, Washington DC 20037.
Insights
Magnesium deficiency in hamsters causes cardiomyopathy. Nifedipine reduced lesions, while digoxin worsened them, supporting the calcium overload hypothesis.
Area of Science:
- Cardiovascular Research
- Nutritional Science
- Cellular Physiology
Background:
- Dietary magnesium deficiency (MD) induces cardiomyopathy (CM) in hamsters.
- Pathological features include myocardial necrosis, calcification, and inflammatory cell infiltration.
- The underlying mechanism is hypothesized to involve calcium (Ca) overload secondary to sodium (Na) accumulation.
Purpose of the Study:
- To investigate the role of (Na.K)-ATPase inhibition and Na-Ca exchange in magnesium-deficient cardiomyopathy (MDCM).
- To test the therapeutic potential of nifedipine and digoxin in a hamster model of MDCM.
Main Methods:
- Hamsters were fed a magnesium-deficient diet and treated with nifedipine, digoxin, or placebo.
- Cardiac lesions were quantified after 14 days using histological analysis.
- Dose-dependent effects of nifedipine and digoxin on lesion severity were assessed via regression analysis.
Main Results:
- Nifedipine administration resulted in a dose-dependent reduction in the abundance and diameter of myocardial lesions.
- Digoxin treatment led to a dose-dependent increase in both the abundance and diameter of MDCM lesions.
- These findings indicate opposing effects of the tested drugs on lesion development.
Conclusions:
- The results support the hypothesis that magnesium-deficient cardiomyopathy is linked to calcium overload.
- Inhibition of cardiac myocyte (Na.K)-ATPase plays a crucial role in the pathogenesis of MDCM.
- Pharmacological interventions targeting ion transport mechanisms may modulate the progression of MDCM.
Abstract:
Hamsters fed a Mg-deficient diet (MD) develop a cardiomyopathy (CM) with foci of myocardial necrosis, calcification, and modest mononuclear and giant cell infiltration. We hypothesize that the lesions are secondary to Ca overload following an increase in myocardial Na due to inhibition of (Na.K)-ATPase and secondary Na-Ca exchange. Nifedipine and digoxin were selected as agents to test this hypothesis. Hamsters were given nifedipine, digoxin, or placebo as sustained release subcutaneous pellets the same day they were started on the MD diet. Animals were killed after 14 days, and MD lesions were quantified in H&E stained slides. Regression analysis showed that nifedipine produced a dose-dependent reduction in lesion abundance (p less than .005) and diameter (p less than .05), while digoxin produced a dose-dependent increase in lesion abundance (p less than .005) and diameter (p less than .005). These results support the hypothesis that MDCM is secondary to Ca overload coupled to inhibition of (Na.K)-ATPase of cardiac myocytes.