Genetic variability in response to dietary calcium

Area of Science:

• Nutritional Physiology
• Cardiovascular Research
• Genetics

Background:

• Dietary calcium supplementation can lower blood pressure in hypertensive rats.
• Calcium-restricted diets can elevate blood pressure, especially with sodium restriction.
• These effects are linked to changes in serum ionized calcium concentrations.

Purpose of the Study:

• To investigate the influence of altered dietary calcium and sodium on blood pressure in genetically normotensive rats.
• To determine if blood pressure responses to dietary changes vary across different rat strains.

Main Methods:

• Three rat strains (Fisher 344, Wistar Furth, ACI) were fed either low (0.1% Ca, 0.25% Na) or normal (1.0% Ca, 0.45% Na) diets from 4 to 29 weeks of age.
• Systolic blood pressure was measured indirectly.
• Serum electrolytes (ionized calcium, phosphorus, magnesium) were analyzed.

Main Results:

• Only Fisher 344 rats consistently showed elevated blood pressure on low calcium/low sodium diets.
• All strains exhibited reduced ionized calcium and increased phosphorus and magnesium on restricted diets.
• In Fisher 344 rats, blood pressure correlated inversely with ionized/total calcium and positively with phosphorus/magnesium; no such correlations were found in other strains.

Conclusions:

• Significant genetic variability exists in blood pressure responses to dietary calcium and sodium alterations.
• Diet-induced changes in serum electrolytes, particularly calcium, do not always predict blood pressure changes.
• Strain-specific differences in calcium-sensitive physiological processes likely mediate blood pressure regulation.