Objective: The purpose of this study was to compare the effects of conjugated equine estrogens (CEE) and estradiol benzoate on the blood pressure and body weight of spontaneously hypertensive rats (SHRs) and the associated changes in several components of the natriuretic peptide system.
Methods: The blood pressure of randomly distributed female SHRs and Wistar rats was determined by tail plethysmography. The rats were ovariectomized and, after 3 weeks, injected daily for 4 days with estradiol benzoate (5 μg/100 g/d), CEE (50 μg/100 g/d), or vehicle (corn oil 0.1 mL/100 g/d). One day after the last injection, the rats were decapitated, and their blood was collected to measure atrial natriuretic peptide (ANP) and estradiol. The atria were removed to measure ANP levels using radioimmunoassay and to quantify ANP messenger RNA expression using real-time polymerase chain reaction. The kidneys and adipose tissue were removed to analyze the expression of natriuretic peptide clearance receptor messenger RNA.
Results: A reduction in blood pressure was observed in estradiol-treated SHRs, but CEE treatment had no effect. Estradiol decreased the body weight and parametrial adipose tissue mass of SHRs. Estradiol-induced alterations in SHRs were accompanied by increased synthesis and release of ANP. CEE had no effect on body weight but increased the mesenteric adipose tissue mass of SHRs.
Conclusions: These results indicate that estradiol and CEE have different effects on the reduction in body weight and blood pressure. These results are correlated with changes in plasma ANP levels.
From the 1Department of Physiology and Biophysics, Instituto de Ciencias Biologicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil; and 2Multidisciplinary Institute of Health, Universidade Federal da Bahia, Vitória da Conquista, BA, Brazil.
Received May 24, 2012; revised and accepted September 28, 2012.
Funding/support: This work was financially supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico, Fundação da Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, and Fundação de Amparo à Pesquisa do Estado de Minas Gerais. Pro-Reitoria de Pesquisa of the Universidade Federal de Minas Gerais paid for the cost of English correction.
Financial disclosure/conflicts of interest: None reported.
Address correspondence to: Adelina Martha Reis, PhD, Departamento de Fisiologia e Biofisica, Instituto de Ciencias Biologicas, Universidade Federal de Minas Gerais, Av. Antonio Carlos, 6627, CEP 31270-901 Belo Horizonte, MG, Brazil. E-mail: firstname.lastname@example.org