The effects of dietary sodium and moderate exercise on sodium-induced hypertension in Dahl salt-sensitive rats

Abstract

It was hypothesized that in the genetically predisposed salt-sensitive rat, there would be an interactive relationship between the level of dietary sodium, the level of moderate physical exercise, and blood pressure. The level of sodium intake studied (4% of the diet) compared to that of the average dietary intake of sodium reported for people in the United States. The exercise studied was walking, the regimen most commonly used by people in the United States. The hypotheses tested were: (1) A 4% sodium diet would demonstrate a significant decrease in mortality and an increase in life span as compared to an 8% sodium diet in Dahl Salt-sensitive (Dahl-S) rats. (2) Walking, as a form of exercise, would significantly reduce systolic blood pressure in hypertension induced by a 4% sodium diet in Dahl-S rats. (3) In mature Dahl-S rats which had subsisted on a 4% sodium diet, had no exercise regimen, and whose systolic blood pressures exceeded 200 mmHg, when dietary sodium content was reduced from 4% to 0.4%, there would be a difference in systolic blood pressures between groups which underwent exercise and those which did not exercise. Hypothesis #1 was shown to be true. By reducing the sodium in the diet from 8% to 4%, mortality significantly decreased and rats lived significantly longer. Hypothesis #2 was shown to be false. Results indicated that moderate exercise did not reduce or control sodium-induced hypertension. It was observed that exercise did improve glomeruler filtration significantly in the rats that exercised while receiving the high (4%) sodium diet. Hypothesis #3 was shown to be false. In the mature rats, reduction of sodium in the diet from 4% to 0.4%, and the imposition of exercise upon one of the two groups, resulted in a slight decrease in hypertension in both groups. No statistically significant differences in systolic blood pressures were found between the exercise and no-exercise groups. Moderate exercise was ineffectual in reducing systolic blood pressures even after the 4% sodium diet was replaced with the 0.4% sodium diet.