title: Effect of ovariectomy on blood pressure and venous tone in female spontaneously hypertensive rats.
abstract: BACKGROUND
  Venous capacitance plays an important role in circulatory homeostasis. A number of reports have suggested an effect of estrogen on venous function. This study tested the hypothesis that ovariectomy would increase venous tone in the female spontaneously hypertensive rat (SHR) via autonomic mechanisms.
  
  
  METHODS
  Five-week-old female SHR were subjected to sham operation (Sham) or ovariectomy (OVX). At 10 weeks of age, the rats were instrumented for the measurement of arterial and venous pressure. A balloon catheter was advanced into the right atrium. Mean circulatory filling pressure (MCFP), an index of venous tone, was calculated. Mean arterial pressure (MAP), heart rate (HR), and MCFP were recorded from conscious rats. Postsynaptic adrenergic responsiveness was assessed by constructing cumulative dose-response curves to norepinephrine (NE).
  
  
  RESULTS
  MAP was not significantly affected by ovariectomy (Sham 127 +/- 6 mm Hg vs. OVX 130 +/- 3 mm Hg). HR also was not different between groups (Sham 409 +/- 11 bpm vs. OVX 399 +/- 12 bpm). Conversely, MCFP was significantly, but moderately, increased in OVX SHR (Sham 5.2 +/- 0.2 mm Hg vs. OVX 5.9 +/- 0.2 mm Hg). Ganglionic blockade produced marked decreases in MAP, HR, and MCFP in both groups; however, the responses were not different between groups. Infusion of NE caused dose-dependent increases in MAP and MCFP. There were no statistically significant differences in these responses between Sham and OVX SHR.
  
  
  CONCLUSIONS
  Endogenous ovarian hormones effect a small reduction in MCFP. This effect does not appear to be mediated by adrenergic mechanisms.
authors.affiliation: Basic Biomedical Sciences, University of South Dakota Sanford School of Medicine, Vermillion, South Dakota, USA. dsmartin@usd.edu
authors.forename: Douglas S
authors.initials: DS
authors.lastname: Martin
authors.forename: Rebecca
authors.initials: R
authors.lastname: Redetzke
authors.forename: Erin
authors.initials: E
authors.lastname: Vogel
authors.forename: Connie
authors.initials: C
authors.lastname: Mark
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Eyster
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006973:Hypertension / Q000503:physiopathology*; D009131:Muscle, Smooth, Vascular / Q000503:physiopathology*; D009638:Norepinephrine / Q000494:pharmacology; D010052:Ovariectomy; D010053:Ovary / Q000502:physiology*; D051381:Rats; D011918:Rats, Inbred SHR; D013564:Sympathetic Nervous System / Q000502:physiology; D014680:Veins / Q000503:physiopathology
chemical_list: D009638:Norepinephrine