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Effects of ovariectomy on the secretory apparatus in the right atrial cardiomyocytes of middle-aged mice.

Souza RR, Oliveira VC, Curi TC, Maldonado DC - Clinics (Sao Paulo) (2014)

Bottom Line: Systolic blood pressure was measured after ovariectomy (9 mo of age) and at the moment of sacrifice (12 mo of age).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.These findings suggest a pool with a low turnover rate, i.e., low synthesis and elimination of natriuretic peptides.

View Article: PubMed Central - PubMed

Affiliation: ICB-USP and Department of Biology, Department of Anatomy, São Judas Tadeu University, São Paulo, SP, Brazil.

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.

Conclusion: 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.

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Related in: MedlinePlus

Electronic photomicrographs of sections obtained from RA cardiomyocytes of mice from the sham (A) and OVX (B) groups showing the nucleus (N) with euchromatin (white arrows) and the pores of the nuclear membrane (black arrows).
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f3-cln_69p554: Electronic photomicrographs of sections obtained from RA cardiomyocytes of mice from the sham (A) and OVX (B) groups showing the nucleus (N) with euchromatin (white arrows) and the pores of the nuclear membrane (black arrows).

Mentions: In the cardiomyocytes obtained from the mice in the two groups, the euchromatin appeared disperse and not readily stainable, whereas the heterochromatin appeared as a narrow peripheral band near the nuclear membrane (Figure 3). The cross sections show the typical structure of the nuclear envelope with two parallel membranes and the nuclear pores as electron-dense structures embedded in the spaces where the inner and outer nuclear membranes join together (Figure 3). The density of the pores in the nuclear membrane and the relative volume of nuclear euchromatin were significantly lower in the RA cardiomyocyte obtained from the OVX group compared with the sham group (p<0.05) (Table 2).


Effects of ovariectomy on the secretory apparatus in the right atrial cardiomyocytes of middle-aged mice.

Souza RR, Oliveira VC, Curi TC, Maldonado DC - Clinics (Sao Paulo) (2014)

Electronic photomicrographs of sections obtained from RA cardiomyocytes of mice from the sham (A) and OVX (B) groups showing the nucleus (N) with euchromatin (white arrows) and the pores of the nuclear membrane (black arrows).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4129560&req=5

f3-cln_69p554: Electronic photomicrographs of sections obtained from RA cardiomyocytes of mice from the sham (A) and OVX (B) groups showing the nucleus (N) with euchromatin (white arrows) and the pores of the nuclear membrane (black arrows).
Mentions: In the cardiomyocytes obtained from the mice in the two groups, the euchromatin appeared disperse and not readily stainable, whereas the heterochromatin appeared as a narrow peripheral band near the nuclear membrane (Figure 3). The cross sections show the typical structure of the nuclear envelope with two parallel membranes and the nuclear pores as electron-dense structures embedded in the spaces where the inner and outer nuclear membranes join together (Figure 3). The density of the pores in the nuclear membrane and the relative volume of nuclear euchromatin were significantly lower in the RA cardiomyocyte obtained from the OVX group compared with the sham group (p<0.05) (Table 2).

Bottom Line: Systolic blood pressure was measured after ovariectomy (9 mo of age) and at the moment of sacrifice (12 mo of age).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.These findings suggest a pool with a low turnover rate, i.e., low synthesis and elimination of natriuretic peptides.

View Article: PubMed Central - PubMed

Affiliation: ICB-USP and Department of Biology, Department of Anatomy, São Judas Tadeu University, São Paulo, SP, Brazil.

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.

Conclusion: 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.

Show MeSH
Related in: MedlinePlus