Published Online
on March 24, 2003

A more recent version of this article appeared on May 1, 2003

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Submitted on January 14, 2003
Revised on February 4, 2003

Estrogen Depletion Increases Blood Pressure and Hypothalamic Norepinephrine in Middle-Aged Spontaneously Hypertensive Rats

Ning Peng; John T. Clark; Chi-Chang Wei; and J. Michael Wyss^*

From the Departments of Cell Biology (N.P., J.M.W.) and Physiology and Biophysics (C.-C.W.), University of Alabama at Birmingham, Ala; and Department of Anatomy and Physiology, Meharry Medical College (J.T.C.), Nashville, Tenn.

^* To whom correspondence should be addressed. E-mail: jmwyss{at}uab.edu.

Abstract--In male spontaneously hypertensive rats (SHR) a high NaCl diet increases arterial pressure via a reduction in anterior hypothalamic nucleus norepinephrine release. Young female SHR are relatively well protected from this NaCl-sensitive hypertension, but depletion of both endogenous and dietary estrogens greatly exacerbates NaCl-sensitive hypertension. This study tests the hypothesis that estrogen also protects late middle-aged female SHR from NaCl-sensitive hypertension and that this effect is mediated by an estrogen-related effect on hypothalamic norepinephrine release. Ten-month-old female SHR were ovariectomized and placed on a phytoestrogen-free diet containing either basal or high NaCl. Each rat was implanted with a silastic tube containing 17 estradiol or vehicle. Three months later, arterial pressure and hypothalamic norepinephrine metabolite levels (MOPEG) were measured. On the basal NaCl diet, estrogen-depleted rats displayed increased arterial pressure (12 mm Hg) and decreased anterior hypothalamic nucleus MOPEG (20%). Both effects were reversed by estrogen treatment. In all groups, the high NaCl diet increased arterial pressure by over 35 mm Hg and reduced anterior hypothalamic nucleus MOPEG by >60%. Across all groups, there was a significant inverse correlation between arterial pressure and anterior hypothalamic nucleus MOPEG. These data suggest that both dietary NaCl excess and estrogen depletion raise arterial pressure in middle-aged female SHR by a decreasing hypothalamic norepinephrine.

Key words: estrogen • norepinephrine • sodium • sympathetic nervous system • blood pressure

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