The Effects of Dietary Sodium on Hypertension and Stroke Development in Female Stroke-Prone Spontaneously Hypertensive Rats

Previous studies on male stroke-prone spontaneously hypertensive rats (SHRSP) have shown that a high-salt diet accelerated the onset of hypertension and stroke, resulting in an increased mortality rate at a younger age. The purpose of this study was to examine whether a similar effect is present in female SHRSP. After weaning at 4 weeks of age, 32 female SHRSP were placed on a Japanese-style rat diet containing either 0.3% NaCl or 4% NaCl. Blood pressure (BP), heart rate, and body weight were measured weekly. Beginning at 9 weeks of age, the SHRSP on the 4% NaCl diet began to show a consistently and significantly higher BP than those in the 0.3% NaCl group, reaching an average BP of 245 +/- 9 mmHg at 16 weeks of age as compared to 184 +/- 3 mmHg in the 0.3% NaCl group. Some female SHRSP in the 4% NaCl group started to exhibit behavioral signs of stroke at 12 weeks of age and 100% mortality was found by 20 weeks. There was 0% mortality in the 0.3% NaCl group at that age. A positive correlation was found between the age at which BP surpassed 220 mmHg and the age death occurred due to stroke. No significant difference was noted in the heart rate or body weight measurements between the two groups. The increased mortality rate in the 4% NaCl diet group was accompanied by organ damage as evidenced by the presence of left ventricular hypertrophy, edematous kidneys, renal malfunction, kidney lesions, and cerebral lesions in these female SHRSP. It is concluded that a high-salt diet exacerbates hypertension and caused an increased mortality rate. This increased mortality rate was associated with an increased left ventricular hypertrophy, kidney damage and subsequent malfunction, and cerebrovascular lesions in these female SHRSP.