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Role of sodium in hypertensive cardiac hypertrophy
Insights
Dietary sodium restriction reduced cardiac hypertrophy in hypertensive rats without lowering blood pressure. This suggests factors beyond blood pressure, like sodium intake, influence heart enlargement and sympathetic nervous system activity.
Area of Science:
- Cardiology
- Nephrology
- Physiology
Background:
- Systemic hypertension can lead to cardiac hypertrophy, a thickening of the heart muscle.
- The exact mechanisms driving cardiac hypertrophy are complex and may involve factors beyond elevated blood pressure (afterload).
- Previous research suggests non-hemodynamic factors influence cardiac hypertrophy.
Purpose of the Study:
- To investigate the impact of dietary sodium restriction on cardiac hypertrophy in a rat model of renal hypertension.
- To determine if sodium intake influences cardiac hypertrophy independently of its effect on blood pressure.
- To explore the role of the sympathetic nervous system in this model.
Main Methods:
- Utilized the two-kidney one-clip (2K1C) rat model to induce renal hypertension.
- Established hypertension with a normal diet, then introduced a sodium-deficient diet in one experimental group.
- Measured systolic blood pressure and relative heart weight; assessed tissue catecholamine levels.
Main Results:
- Hypertensive rats on a normal diet exhibited significantly elevated systolic blood pressure and increased relative heart weight.
- Sodium restriction did not reverse hypertension but significantly reduced relative heart weight compared to controls.
- Cardiac hypertrophy in rats on a regular diet showed depressed norepinephrine levels, which normalized with sodium restriction.
Conclusions:
- Demonstrated a dissociation between blood pressure and cardiac hypertrophy in the 2K1C rat model.
- Supports the hypothesis that factors other than blood pressure, specifically dietary sodium intake, contribute to cardiac hypertrophy.
- Suggests a potential role for the sympathetic nervous system in mediating these effects.
Abstract:
Cardiac hypertrophy in systemic hypertension may not result simply from increased afterload. Previous studies indicate that factors other than blood pressure may influence cardiac hypertrophy. We evaluated the effects of dietary sodium restriction in two-kidney one-clip renal hypertensive rats. After the renal artery had been clipped, the rats received a normal diet until hypertension was established; thereafter, a sodium-deficient diet was instituted in one group. Clipped rats on a regular diet had significantly higher systolic blood pressures than sham-operated controls (205 +/- 9 vs. 129 +/- 1 mm Hg, respectively). Sodium restriction did not reverse hypertension (190 +/- 8 mm Hg), but led to a significant reduction of relative heart weight compared to rats on the normal diet (2.94 +/- 0.24 vs. 3.86 +/- 0.23 mg/g, respectively; P less than 0.01). The hypertrophied hearts of animals on the regular diet showed depressed tissue catecholamines (significant only for norepinephrine); sodium restriction resulted in a restoration to normal levels. Thus, we demonstrated a dissociation of blood pressure and cardiac hypertrophy in the two-kidney one-clip model, similar to previous findings in other models. Our results support the concept that factors other than blood pressure contribute to cardiac hypertrophy. Dietary sodium intake appears to be one such factor. In addition, a possible role of the sympathetic nervous system is suggested.