The increase in renal sodium excretion in response to Angiotensin II infusion in exercised female rats is dependent on a rise in renal perfusion pressure.

Abstract

Prior studies in this lab have shown that chronically exercised female spontaneously hypertensive rats (SHR) and Wistar‐Kyoto (WKY) rats excrete a greater amount of sodium in response to angiotensin II infusion than do sedentary rats. The current study determined if the difference in renal sodium excretion persisted when the renal perfusion pressure (RPP) was held constant. Female SHR and female WKY rats were separated into sedentary and exercise groups at 4 weeks of age. The exercise group voluntarily exercised for at least eight weeks using an exercise wheel and time/distance monitor. At 13 weeks of age or older, rats were anesthetized and catheters were placed into the jugular vein, and carotid and femoral arteries. A noose, placed around the abdominal aorta, was continually adjusted to maintain a constant RPP during Ang II infusion. Ang II was infused at 0, 0.125, 0.5, and 2µg/ml saline, each for 15 minutes. MAP and RPP were measured continually. Urine was collected during each 15 minute period and analyzed for sodium excretion. Sodium excretion did not significantly increase with the Ang II infusions when RPP was held constant, and no difference was found between the exercised and sedentary rats. The increase in renal sodium excretion observed in exercised female rats compared to sedentary appears to be due to a difference in the pressure natriuresis response. Funding: Department of Biological Sciences, MSU, M.