1. ATRIAL NATRIURETIC PEPTIDE (ANP) SYSTEM IN RAT POLYCYSTIC OVARIES
1Pereira VM, 2Reis FM, 1Martins AS, 1Reis AM.
1Dept of Physiology and Biophysics, Institute of Biological Sciences, 2Dept of Obstetrics and Gynecology, Faculty of Medicine,
Federal University of Minas Gerais, Belo Horizonte, Brazil
Plasma and Ovarian Estradiol Concentration
ABSTRACT
Immunohistochemistry for ANP
Plasma Estradiol (pg/ml) 2 4 6 8
Control
(n = 6)
PCO
(n = 8)
Ovarian Estradiol (pg/mg)
0.0
0.5
1.0
1.5
2.0 *
(P<0.05)
Polycystic ovaries are often associated with acyclicity, hyperandrogenism and subfertility. In women, they are part of the spectrum of the polycystic ovary syndrome (PCOS)[1]. Evidence suggests the involvement of paracrine factors in the pathogenesis of polycystic ovaries. Atrial natriuretic peptide (ANP), besides its well known role in fluid and salt balance, has also been described in ovaries and testis, where it participates in steroid hormone production and oocyte maturation[2,3,4].
Control
(estrus) a b c
PCO
OBJECTIVE
Plasma and Ovarian Testosterone Concentration
The aim of this study was to determine the modulation of the Natriuretic Peptide System in rat polycystic ovaries. d e f
Plasma Testosterone (ng/ml)
0.00
0.10
0.20
0.30
PCO
(n = 8)
(n = 6)
Control
Ovarian Testosterone (ng/mg)
0.02
0.04
0.06
0.08 *
(P<0.05)
Control ovaries: ANP immunoreactivity (brown color) in theca-interstitial cells, granulosa cells of antral follicles (a,b), and luteal cells (c). Polycystic ovaries: ANP-immunostaining predominantely to theca-interstitial compartment (d,e,f-arrows).
METHODS
Polycystic ovaries were induced in adult female rats by a single sc injection of estradiol valerate (2 mg/rat), while a control group received oil vehicle[5]. Sixty days later the rats were killed and their ovaries were quickly removed and used in different protocols:
 Immunohistochemistry was carried out in paraffin-embedded ovarian sections using a polyclonal antibody anti-ANP;
 Ovarian ANP concentration was measured by radioimmunoassay (RIA);  Neutral endopeptidase (NEP) activity was determined in ovarian homogenates by spectrofluorometric assay;
 Real-time PCR was used to detect mRNA expression of ANP and GC-A and C receptors in ovarian homogenates;
 Binding-autoradiography for ANP receptors was performed in frozen ovarian sections incubated with 125I-ANP;
 Ovarian estradiol and testosterone concentrations were measured by RIA.
Binding-autoradiography for GC-A and C receptors in rat ovary
CONCLUSIONS
This study shows that ANP and receptors are expressed and down- regulated in a rat model of polycystic ovaries. The presence of ANP in theca-interstitial cells suggests a paracrine role for it in the modulation of androgen secretion, a critical mechanism for understanding the pathogenesis of PCOS.
RESULTS
Real-Time PCR for ANP and GC-A and C receptors in rat ovary
REFERENCES
ANP (pg/mg) 2 4 6 8 10
Control
PCO *
(P<0.01)
(n = 6)
NEP activity (g/min/mg)
(P<0.05)
0.0
0.1
0.2
0.3
0.4
0.5
PCO
Control
(n = 6) *
Relative ANP mRNA (AU)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Control
PCO
(n = 4)
(n = 3)
Relative GC-A mRNA (AU)
1.4
1.6
1.8
2.0
Relative C Receptor mRNA (AU) *
(P<0.05)
1) Franks S. Polycystic Ovary Syndrome. New Engl J Med 1995;333:
2) Gutkowska et al. The atrial natriuretic peptide system in rat ovaries. Endocrinology 1993;132:
3) Brenner et al. Diverse biological actions of atrial natriuretic peptide. Physiol Rev 1990;70:
4) Pereira et al. Regulation of steroidogenesis by atrial natriuretic peptide (ANP) in the rat testis: differential involvement of GC-A and C receptors. Peptides 2008;29:
5) Brawer et al. Development of Polycystic Ovarian Condition (PCO) in the estradiol valerate-treated rat. Biol Reprod 1986;35: .
Financial support: CAPES, CNPq, FAPEMIG