Estrogen depletion increases blood pressure and hypothalamic norepinephrine in middle-aged spontaneously hypertensive rats.
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 17beta 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.
Peng
Ning
N
Department of Cell Biology, University of Alabama at Birmingham, Birmingham, Ala 35294-0006, USA.
Clark
John T
JT
Wei
Chi-Chang
CC
Wyss
J Michael
JM
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D004958:Estradiol / Q000097:blood / Q000494:pharmacology; D004967:Estrogens / Q000172:deficiency*; D005260:Female; D006973:Hypertension / Q000378:metabolism / Q000503:physiopathology*; D007032:Hypothalamus, Anterior / Q000187:drug effects / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism*; D010052:Ovariectomy; D051381:Rats; D011918:Rats, Inbred SHR; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage
D004967:Estrogens; D017673:Sodium Chloride, Dietary; D004958:Estradiol; D009638:Norepinephrine