The Effect of Exercise on Kidney Salt Excretion in Female Hypertensive Rats

Hypertension, or high blood pressure, affects approximately 33% of the U.S. population. If untreated, hypertension can lead to heart disease, kidney disease, stroke, and other pathologies. A majority contributor to hypertension is the inability of the kidneys to properly eliminate sodium (salt) from the body when blood pressure elevates. This relationship between blood pressure and urinary sodium excretion is known as the pressure-natriuresis curve, which is altered in hypertensive patients. Exercise is commonly recommended as a prevention or treatment for hypertension. Although exercise does lower blood pressure, the exact effect of exercise on the pressure natriuresis curve, is unclear. In this study, female spontaneously hypertensive rats SHR rats were exercised voluntarily from 4 to 12 weeks of age, using an exercise wheel and counter. At 12 weeks of age, the rats were anesthetized, and the urine sodium excretion was determined at different levels of blood pressure, 20 mmHg below the baseline and 30 mmHg above baseline. Urine samples were collected in 15 min intervals and analyzed for sodium content by flame photometer. A pressure-natriuresis curve was generated by graphing the relationship between the excretion of sodium from the urine and the blood pressure. The curve was compared between exercised and sedentary rats and a steeper slope was found in the exercise group. Furthermore, the exercised rats excreted more sodium at any level of blood pressure. This shows that exercise improves the excretion of sodium in the urine, and this may contribute to the blood pressure lowering effects of exercise