title: Effects of ovariectomy on the secretory apparatus in the right atrial cardiomyocytes of middle-aged mice.
abstract: OBJECTIVE
  The aim of the present study was to evaluate the effects of ovariectomy on the secretory apparatus of natriuretic peptides in right atrial cardiomyocytes.
  
  
  METHODS
  Nine-month-old mice underwent bilateral ovariectomy or sham surgery. The blood exam of the ovariectomized mice showed results consistent with castrated females. Systolic blood pressure was measured after ovariectomy (9 mo of age) and at the moment of sacrifice (12 mo of age). Fragments of the right atrium were collected and prepared for electron microscopy examination. The following variables were quantified: the quantitative density and area of the natriuretic peptide granules, the relative volume of euchromatin in the nucleus, the number of pores per 10 μm of the nuclear membrane and the relative volumes of the mitochondria and Golgi complex.
  
  
  RESULTS
  The cardiomyocytes obtained from ovariectomized mice indicated that the quantitative density and the area of secretory granules of natriuretic peptides were significantly lower compared with the sham-operated mice. Furthermore, there was a decrease in the relative volume of euchromatin, a lower density of nuclear pores, and lower relative volumes of the mitochondria and Golgi complex in the ovariectomized mice compared with the sham-operated mice. These findings suggest a pool with a low turnover rate, i.e., low synthesis and elimination of natriuretic peptides.
  
  
  CONCLUSIONS
  A lack of estrogen caused hypotrophy of the secretory apparatus in right atrial cardiomyocytes that could explain the weak synthesis of natriuretic peptides in mice. Furthermore, one of the mechanisms of blood pressure control was lost, which may explain, in part, the elevated blood pressure in ovariectomized mice.
authors.affiliation: ICB-USP and Department of Biology, Department of Anatomy, São Judas Tadeu University, São Paulo, SP, Brazil.
authors.forename: Romeu R de
authors.initials: RR
authors.lastname: Souza
authors.affiliation: Departament of Anatomy, São Judas Tadeu University, São Paulo, SP, Brazil.
authors.forename: Vanessa C de
authors.initials: VC
authors.lastname: Oliveira
authors.affiliation: Institute of Physical Activity Sciences and Sports, Cruzeiro do Sul University.
authors.forename: Tania Cristina P
authors.initials: TC
authors.lastname: Curi
authors.affiliation: Department of Anatomy, Federal University of São Paulo, Department of Morphology and Genetics and Nove de Julho University, São Paulo, SP, Brazil.
authors.forename: Diogo C
authors.initials: DC
authors.lastname: Maldonado
mesh_terms: D000818:Animals; D009320:Atrial Natriuretic Factor / Q000032:analysis / Q000187:drug effects*; D001794:Blood Pressure; D004958:Estradiol / Q000097:blood; D004967:Estrogens / Q000502:physiology; D022041:Euchromatin / Q000648:ultrastructure; D005260:Female; D006056:Golgi Apparatus / Q000648:ultrastructure; D006325:Heart Atria / Q000166:cytology; D008810:Mice, Inbred C57BL; D053142:Mitochondrial Size; D023421:Models, Animal; D032383:Myocytes, Cardiac / Q000648:ultrastructure*; D022022:Nuclear Pore / Q000648:ultrastructure; D010052:Ovariectomy / Q000009:adverse effects*
chemical_list: D004967:Estrogens; D022041:Euchromatin; D004958:Estradiol; D009320:Atrial Natriuretic Factor