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Effect of calcium diet on the vascular reactivity of DOCA-salt hypertensive rats
1Department of Medical Research Taipei Veterans General Hospital, Taiwan, R.O.C.
Insights
Dietary calcium intake lowered blood pressure in hypertensive rats, but did not fully prevent hypertension. Vascular reactivity changes suggest the sodium-potassium pump may be involved in calcium
Area of Science:
- Cardiovascular Physiology
- Nutritional Science
Background:
- Dietary calcium intake is known to influence blood pressure.
- Hypertension, particularly DOCA-salt induced hypertension, presents challenges in vascular regulation.
Purpose of the Study:
- To investigate the impact of dietary calcium on blood pressure and vascular reactivity in DOCA-salt hypertensive rats.
- To explore the mechanisms underlying calcium's effect on vascular smooth muscle function.
Main Methods:
- DOCA-salt hypertensive rats were fed a calcium-supplemented diet for four weeks.
- Blood pressure was monitored throughout the study period.
- Vascular reactivity of tail artery helical strips to norepinephrine (NE), potassium chloride (KCl), and arginine vasopressin (AVP) was assessed in vitro in normal and calcium-free media.
Main Results:
- Calcium feeding significantly decreased blood pressure but did not completely prevent hypertension development.
- Vascular responses to NE, KCl, and AVP in normal calcium medium showed no significant differences between groups.
- In calcium-free medium, significant differences in responses to NE and AVP were observed.
- Calcium-fed rats exhibited reduced responsiveness to K+-induced relaxation, suggesting altered Na+-K+ pump activity.
Conclusions:
- Dietary calcium has a hypotensive effect in DOCA-salt hypertensive rats.
- The altered vascular reactivity in calcium-fed rats, particularly in calcium-free conditions and with K+-induced relaxation, suggests a role for the Na+-K+ pump.
- Changes in vascular reactivity to agonists may be less significant than other mechanisms in mediating the blood pressure-lowering effect of dietary calcium.
Abstract:
It has been demonstrated that an increase in dietary calcium intake can lower the blood pressure of the hypertensives. We examined the effect of dietary calcium on blood pressure and vascular reactivity in DOCA-salt hypertensive rats. Blood pressure was significantly decreased after four weeks of calcium feeding. Nevertheless, the development of hypertension was not completely avoided. There was no difference between the calcium fed group and the control group in their response to NE, KCl and AVP in tail artery helical strips in normal calcium medium in vitro. However, the responses of these two groups to NE (10(-6) M) and AVP (10mU) were significantly different in Ca2+-free medium. Furthermore, the tail artery from Ca-fed group was less responsive to K+-induced relaxation. Since K+-induced relaxation has been applied to indicate the activity of Na+-K+ pump, we suggest that the activity of Na+-K+ pump may be involved and that the change in vascular reactivity to agonists might be rather insignificant in lowering the blood pressure of Ca-fed DOCA-salt hypertensive rats.