Ovariectomy induces NaCl-sensitivity in female spontaneously hypertensive rats

Academic Article

Abstract

  • Using a telemetry blood pressure monitoring system, we have reported that male spontaneously hypertensive rats (SHR) are NaCl-sensitive, manifesting significant increases in 24-hr MAP when exposed to high dietary NaCl, while female SHR are NaCl-resistant, manifesting no significant change in MAP when exposed to high dietary NaCl. In the current study, a radio frequency pressure transducer (Data Sciences, St. Paul, MN) was implanted into the distal aorta of 10-vk old female SHR, allowing for 24-hr blood pressure and heart rate monitoring (sample frequency even 4 min). At the lime of instrumentation, 24 animals were ovariectomized and 6 were left intact. Ten days later. 12 ovariectomized rats were implanted with a subcutaneous slow-release progesterone pellet (60 mg/pellet) and 12 with a placebo pellet. Values at baseline (1% NaCl diet) and after 2 weeks of high (8%) NaCl diet were: baseline after 2-wk of 8% NaCl diet group n BW 24-hr MAP 24-hr HR BW 24-hr MAP 24-hr HR (g) (mmHg) (bom) (g) (mmHg) (bpm) intact 6 175±4 132±1 353±3 199±3 * 137±3 321±4 * O+placebo 12 191±2 # 127±1 358±3 223±3 *# 135±2 * 318±3 * O+progest 12 190±3 # 127±1 363±3 224±3 *# 138±2 * 323±3 * BW, body weight; MAP, mean arterial pressure; HR, heart rate; O, ovariectomy; progest. progesterone. * different from baseline, p<0.01; # different from intact SHR groups. p<0.01; Serum progesterone levels (measured by radioimmunoassay) at the end of the 2-wk high dietary NaCl exposure were 7.14±2, 4.48±1, and 13.8±3 ng/ml for the intact, ovariectomized+placebo, and ovariectomy+progesterone groups, respectively (all different from one another, p<0.05). These data demonstrate that ovariectomy significantly lowers baseline MAP while inducing NaCl-sensitivity in female SHR. Further, exogenous progesterone does not prevent the NaCl-sensitivity induced by ovariectomy.
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    Author List

  • Zhu ST; Calhoun DA; Chen YF; Oparil S
  • Volume

  • 44
  • Issue

  • 1