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Cardiac physiologic-metabolic changes after chronic low-level heavy metal feeding
The American Journal of Physiology
|July 11, 1980
Summary
This study reveals that chronic exposure to cadmium (Cd) and lead (Pb) in drinking water impacts rat heart function. Cadmium specifically affects the atrioventricular node, while lead impacts the His-Purkinje system, even without obvious toxicity signs.
Area of Science:
- Cardiovascular toxicology
- Environmental health
- Heavy metal effects on cardiac function
Background:
- Chronic exposure to heavy metals like cadmium (Cd) and lead (Pb) is a public health concern.
- Understanding the specific cardiovascular effects of these metals is crucial for risk assessment.
- Previous research indicates potential cardiac impacts, but detailed electrophysiological and metabolic effects require further investigation.
Purpose of the Study:
- To investigate the long-term cardiovascular effects of chronic cadmium and lead exposure in rats.
- To determine the specific impacts of Cd and Pb on cardiac conduction system excitability and conductivity.
- To analyze changes in cardiac phosphate metabolites using phosphorus-31 nuclear magnetic resonance (31P-NMR) spectroscopy.
Main Methods:
- Female Long-Evans hooded rats were exposed to 0 or 5 ppm Cd, Pb, or Cd + Pb in drinking water from weaning to 20 months.
- Indirect blood pressure was measured trimonthly.
- His bundle electrograms (HBE) and electrocardiograms were analyzed.
- Cardiac tissue was analyzed using 31P-NMR spectroscopy to assess phosphate metabolite profiles.
Main Results:
- Growth and organ weights were comparable between heavy metal and control groups.
- Cd selectively depressed conduction system excitability proximal to the common His bundle (atrioventricular node region).
- Pb and Pb + Cd impaired conductivity distal to the common His bundle (His-Purkinje system).
- Cardiac active tension and atrioventricular node excitability were depressed in the Cd group.
- High-energy phosphate and glycerol 3-phosphorylcholine concentrations were reduced in Cd-exposed rats.
Conclusions:
- Chronic exposure to Cd and Pb can induce significant cardiovascular pathophysiological changes.
- These changes occur at the level of the cardiac conduction system (atrioventricular node and His-Purkinje system).
- Metabolic alterations in high-energy phosphates and related compounds are associated with these functional deficits, even in the absence of overt toxicity signs.