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Membrane handling of calcium in essential hypertension
R F Bing1, A M Heagerty, J D Swales
1Department of Medicine, University of Leicester, UK.
Insights
Hypertension is linked to abnormal calcium handling in blood cells, potentially due to altered cell membrane lipids. Supplementing with linoleic acid reduced leucocyte calcium in healthy individuals, suggesting a role for membrane lipids in blood pressure regulation.
Area of Science:
- Cardiovascular Physiology
- Cell Membrane Biology
- Nutritional Science
Background:
- Hypertension is associated with abnormal blood cell calcium handling.
- These abnormalities may stem from alterations in cell membrane lipid composition.
- Previous research suggests a link between ion handling, blood pressure, and membrane lipids.
Purpose of the Study:
- To investigate the role of decreased membrane calcium binding in hypertension.
- To examine the relationship between erythrocyte membrane composition and calcium binding.
- To assess the impact of linoleic acid supplementation on leucocyte calcium levels.
Main Methods:
- Measured basal and maximal calcium binding in hypertensive and normotensive subjects.
- Analyzed erythrocyte membrane composition, focusing on fatty acid ratios.
- Conducted a double-blind crossover trial administering linoleic acid to normotensive volunteers.
Main Results:
- Calcium binding was reduced in both hypertensive subjects and those with a family history of hypertension.
- A negative correlation was found between the palmitic:linoleic acid ratio and calcium binding.
- Linoleic acid administration significantly decreased leucocyte calcium in normotensive volunteers.
Conclusions:
- Reduced membrane calcium binding and altered erythrocyte membrane fatty acid composition are associated with hypertension.
- Linoleic acid may play a role in regulating leucocyte calcium levels.
- Cell membrane lipid variability is a significant factor in calcium handling abnormalities in hypertension.
Abstract:
Several abnormalities have been described in the blood-cell handling of calcium in patients with hypertension and rats with genetic hypertension. We have suggested elsewhere that the multiple abnormalities of monovalent and divalent ion handling by blood cells in hypertension, which are loosely and variably associated with blood pressure, reflect a global variability of cell membrane lipids. In the light of this suggestion we tested the relevance of decreased membrane binding of calcium by examining basal and maximal calcium binding in hypertensive patients and in normotensive subjects with and without a family history of hypertension. Calcium binding was reduced to a similar degree in both hypertensive subjects and those with a family history of hypertension. To examine the role of membrane lipids we examined calcium binding in relation to erythrocyte membrane composition, and found a negative correlation between the palmitic:linoleic acid ratio and calcium binding. This is consistent with the observation of a reduction in the unsaturated fatty acid, linoleic acid, in the erythrocyte membrane of hypertensive subjects, and this may therefore be of functional significance. In further studies, although there was no net difference in leucocyte cytosolic calcium between essential hypertensive subjects and normotensive controls, there was a positive relationship between leucocyte calcium and membrane palmitic:linoleic acid ratio only in normotensives. To test further the role of membrane lipids in calcium handling we administered linoleic acid (4 g daily safflower seed oil) to 13 normotensive volunteers in a double-blind crossover trial. Four weeks of administration of the linoleic acid produced a significant decrease in leucocyte calcium (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)