Angiotensin II is a potent regulator of blood pressure as well as of water and electrolyte balance. Whereas Angiotensin II type 1 receptor (AT1), mediates the vasopressive and aldosterone-secreting effects of angiotensin II, the function of the type-2 receptor is less clear. Yamada et al. (1996) noted, that the AT2 receptor is abundantly expressed in fetus but scantily in adult tissues except brain, adrenal medulla, and atretic ovary. The authors demonstrated that this receptor mediates programmed cell death (apoptosis). They observed this effect in a rat pheochromocytoma cell line and a mouse fibroblast cell line, which express abundant AT2 receptor but not AT1 receptor. The cellular mechanism appeared to involve the dephosphorylation of mitogen-activated protein kinase
NCBI Summary:
The protein encoded by this gene belongs to the G-protein coupled receptor 1 family, and functions as a receptor for angiotensin II. It is an intergral membrane protein that is highly expressed in fetus, but scantily in adult tissues, except brain, adrenal medulla, and atretic ovary. This receptor has been shown to mediate programmed cell death and this apoptotic function may play an important role in developmental biology and pathophysiology. Mutations in this gene are been associated with X-linked mental retardation. [provided by RefSeq, Jan 2010]
Induction of multiple ovulation via modulation of angiotensin II receptors in in vitro ovarian follicle culture models. Kim YJ et al. (2016) In vitro culture of ovarian follicles is a promising bioengineering technique for retrieving fertilizable oocytes from preserved ovarian tissues of cancer survivors. However, current in vitro follicle culture techniques are labour-intensive and of low efficiency, as only single follicle culture (SFC) has been possible to date. The present study investigated the feasibility of multifollicular cluster culture (MFCC) system using angiotensin II receptor (ATII-Rc) analogues. Ovarian pre-antral follicles isolated from 2-week-old C57BL6 mice were cultured with ATII-Rc agonist or antagonist and their maturation outcomes were compared with control group. When single follicles were cultured, the ovulation and maturation rates were similar in all three groups. When three-follicle clusters were cultured, up to three follicles were ovulated in the ATII-Rc agonist group while none or one follicle ovulated in control or antagonist groups (p < 0.0001). Significantly higher numbers of mature oocytes were obtained in the agonist group (three-follicle 28.2 ± 4.9 vs. SFC 11.0 ± 1.3, per 25 cultured droplets) (p < 0.0001), and the development of each fertilized oocytes was comparable to those from SFC. It is therefore concluded that this novel MFCC system can significantly improve the efficiency of in vitro mature oocyte retrieval via ATII-Rc modulation.//////////////////
The Effect of Media Supplementation with Angiotensin on Developmental Competence of Ovine Embryos Derived from Vitrified-warmed Oocytes. Naderi MM et al. (2016) This study was aimed to assess the effects of angiotensin II (Ang II) supplementation to the In Vitro Maturation (IVM) and In Vitro Culture (IVC) media of vitrified-warmed ovine oocytes on their developmental competence and expression of Na(+)/K(+)/ATPase in resulting embryos. The slaughterhouse-derived immature oocytes (n=1069) were randomly distributed into four experimental groups: groups I and II) IVM/IVF and IVC of fresh and vitrified oocytes without angiotensin supplementation (Control-Fresh and Control-Vit groups, respectively); group III) IVM of vitrified oocytes in the presence of Ang II followed by IVF/IVC (Vit-IVM group); and group IV) IVM/IVF of vitrified oocytes followed by IVC wherein the embryos were exposed to Ang II on day 4 of IVC (Vit-D4 group). The embryos were immunostained with primary antibodies against Na(+)/K(+)/ATPase α1 and β1 subunits. In Vit-IVM and Vit-D4 groups, the rates of expanded and total blastocysts on day 7 as well as the proportion of blastocysts on day 8 were increased. The expression of Na(+)/K(+)/ATPase α1 and β1 subunits were positively influenced by the addition of Ang II on day 4 (Vit-D4 group). The addition of Ang II to the IVM and IVC media could improve blastocysts formation in vitrified sheep oocytes. This improvement might be related to the greater expression of Na(+)/K(+)/ATPase α1 and β1 subunits when Ang II was added during IVC.//////////////////
Expression of angiotensin II receptors in the caprine ovary and improvement of follicular viability in vitro. Bruno JB et al. (2015) This study aimed to evaluate mRNA levels of angiotensin II (ANG II) receptors (AGTR1 and AGTR2) in caprine follicles and to investigate the influence of ANG II on the viability and in vitro growth of preantral follicles. Real-time polymerase chain reaction (PCR) was used to quantify AGTR1 and AGTR2 mRNA levels in the different follicular stages. For culture, caprine ovaries were collected, cut into 13 fragments and then either directly fixed for histological and ultrastructural analysis (fresh control) or placed in culture for 1 or 7 days in α-minumum essential medium plus (α-MEM+) with 0, 1, 5, 10, 50 or 100 ng/ml ANG II. Then, the fragments were destined to morphological, viability and ultrastructural analysis. The results showed that primordial follicles had higher levels of AGTR1 and AGTR2 mRNA than secondary follicles. Granulosa/theca cells from antral follicles had higher levels of AGTR1 mRNA than their respective cumulus-oocyte complex (COCs). After 7 days of culture, ANG II (10 or 50 ng/ml) maintained the percentages of normal follicles compared with α-MEM+. Fluorescence and ultrastructural microscopy confirmed follicular integrity in ANG II (10 ng/ml). In conclusion, a high expression of AGTR1 and AGTR2 is observed in primordial follicles. Granulosa/theca cells from antral follicles had higher levels of AGTR1 mRNA. Finally, 10 ng/ml ANG II maintained the viability of caprine preantral follicles after in vitro culture.//////////////////
Angiotensin II type 2 receptor stimulation improves fatty acid ovarian uptake and hyperandrogenemia in an obese rat model of polycystic ovary syndrome. Leblanc S 2014 et al.
Polycystic ovary syndrome (PCOS) is mainly defined by hyperandrogenism, but is also characterized by insulin resistance (IR). Studies showed that overexposure of non-adipose tissues to non-esterified fatty acids (NEFA) may explain both IR and hyperandrogenism. Recent studies indicate that treatment with an angiotensin II type 2 receptor (AT2R) selective agonist improves diet-induced IR. We thus hypothesized that PCOS hyperandrogenism is triggered by ovarian NEFA overexposure and is improved following treatment with an AT2R agonist. Experiments were conducted in 12-week old female JCR:LA-cp/cp rats, which are characterized by visceral obesity, IR, hyperandrogenism and polycystic ovaries. Control JCR:LA +/? rats have a normal phenotype. Rats were treated for 8 days with saline or the selective AT2R agonist C21/M24, and then assessed for: 1) fasting testosterone, NEFA and insulin levels; and 2) an intravenous (18)F-FTHA test to determine NEFA ovarian tissue uptake (Km). Compared to controls, saline-treated PCOS/cp rats displayed higher insulin (100 vs. 5.6 U/mL), testosterone (0.12 vs. 0.04nmol/L), NEFA (0.98 vs. 0.48mmol/L) and Km (20.7 vs. 12.9nmol/gmin) (all P<0.0001). In PCOS/cp rats, C21/M24 did not significantly improve insulin or NEFA, but normalized testosterone (P=0.004) and Km (P=0.009); which were strongly correlated together in all PCOS/cp rats (?=0.74, P=0.009). In conclusion, in an obese PCOS rat model, ovarian NEFA uptake and testosterone levels are strongly associated and are both significantly reduced following short-term C21/M24 therapy. These findings provide new information on the role of NEFA in PCOS hyperandrogenemia and suggest a potential role for AT2R agonists in the treatment of PCOS.
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Kuji et al. (1996) investigated the role of angiotensin II (Ang II) receptor subtypes in gonadotropin-induced ovulation, oocyte maturation, and ovarian steroidogenesis and prostaglandin (PG)
production in in vitro-perfused rabbit ovaries. The addition to the perfusate of PD123319, a nonpeptide Ang II antagonist with a high affinity for AT2 receptors, inhibited hCG-induced ovulation in a dose-dependent manner, whereas CV-11974, a nonpeptide AT1 receptor antagonist, had no effect. The majority of ovulated ova and follicular oocytes resumed meiotic maturation in response to hCG; and PD123319, but not CV-11974, significantly inhibited hCG-induced oocyte maturation. Thus, Ang II produced locally by gonadotropin exposure may be a part of a novel intraovarian paracrine or autocrine control mechanism that operates via the AT2 receptor in the ovary.Li YH, et al reported the localization of angiotensin II in pig ovary and its effects on oocyte maturation in vitro.
The renin-angiotensin system (RAS) has been found in mammalian ovarian tissue; however, its physiological role is unclear. This study examined the content of angiotensin II (Ang II) in porcine follicular fluid (pFF), Ang II localization and its receptors in ovary, and the effects of Ang II on porcine oocyte maturation. The concentrations of Ang II were 6951.82+/-1295.83, 3502.99+/-679.10, 3147.89+/-690.60, and 2545.92+/-407.01pg/ml in pFF from small, medium, large, and extra-large follicles, respectively. In addition, Ang II was found on zona pellucidae (ZP) and granulosa cells by immunoreactive staining. The distribution of AT(1), an Ang II receptor subtype, was in accordance with that of Ang II. However, AT(2), another Ang II receptor, was mainly distributed in the stroma and thecal layers of follicles. When oocytes were cultured in media containing various concentrations of Ang II, a higher (P<0.05) proportion of oocytes reached metaphase II (MII) in the medium with 100ng/ml (87.0%) than without Ang II (61%). When oocytes from different sizes of follicles were separately cultured in media containing 100ng/ml Ang II, maturation rates were significantly higher in oocytes from small (61.5%) and medium (85.1%) follicles than that of their controls (45.1 and 72.6%, respectively). However, addition of Ang II inhibited nuclear maturation in oocytes from large follicles (77.8% versus 87.3%). Fertilization and male pronuclear (MPN) formation rates of oocytes matured in medium containing 100 or 1000ng/ml of Ang II were higher (P<0.05) than that of oocytes matured in medium containing 0 or 10ng/ml Ang II. Glutathione content in oocytes cultured for 44h in medium containing 100 or 1000ng/ml of Ang II was also higher (P<0.01) than that of oocytes cultured in medium containing 0 or 10ng/ml Ang II. In conclusion, Ang II was present in porcine ovaries and may regulate follicle growth and oocyte maturation.
Expression regulated by
FSH, Steroids, Growth Factors/ cytokines
Comment
Pucell et al. (1991) reported that Ang-II receptors (estimated by the specific cell binding of the Ang-II receptor antagonist 125I-Sar1,Ile8,Ang-II) were present on freshly prepared rat granulosa cells and increased by over 2-fold when cultured in serum-free medium for 48 h. FSH prevented the normal increase in Ang-II receptor expression. The inhibitory effect of FSH on granulosa cell Ang-II receptor content was partially mimicked by the cAMP analogue 8-bromo-cAMP, since 8-bromo-cAMP suppressed (by 96%) Ang-II receptor content to a greater extent than FSH (by 60%). Granulosa cell Ang-II receptor content was not modified by progesterone or 17 beta-estradiol, but was decreased by testosterone (by 35%).
REGULATION OF ANGIOTENSIN TYPE 2 RECEPTOR IN BOVINE GRANULOSA CELLS. Portela VM et al. Angiotensin II (AngII) is best known for its role in blood pressure regulation, but it also has documented actions in the reproductive system. There are two AngII receptors, type 1 (AGTR1) and type 2 (AGTR2). AGTR2 mediates the non-cardiovascular effects of AngII, and is expressed in the granulosa cell layer in rodents and is associated with follicle atresia. In contrast, expression of AGTR2 is reported to occur only in theca cells in cattle. The objective of the present study was to determine if AngII also plays a role in follicle atresia in cattle. RT-PCR demonstrated AGTR2 mRNA in both granulosa and theca cells of bovine follicles. The presence of AGTR2 protein was confirmed by immunofluorescence. Abundance of AGTR2 mRNA in granulosa cells was higher in healthy compared to atretic follicles, whereas in theca cells it did not change. Granulosa cells were cultured in serum-free medium, and treatment with hormones that increase estradiol secretion (FSH, IGF1 and bone morphogenetic protein-7) increased AGTR2 mRNA and protein levels, whereas fibroblast growth factors inhibited estradiol secretion and AGTR2 protein levels. The addition of AngII or an AGTR2-specific agonist to granulosa cells in culture did not affect estradiol secretion or cell proliferation, but inhibited abundance of mRNA encoding SerpinE2, a protein involved in tissue remodeling. As estradiol secretion is a major marker of nonatretic granulosa cells, these data suggest that AngII is not associated with follicle atresia in cattle, but may have other specific roles during follicle growth.
Ovarian localization
Oocyte, Granulosa, Theca
Comment
Localization of angiotensin receptor type 2 in fetal bovine ovaries. Portela VM et al. (2016) In the ovary, angiotensin II (ANGII) acts through the type 2 receptor (AGTR2) to induce ovulation and may play a role in follicle atresia. In this study, we determined the expression of AGTR2 mRNA and protein during follicle formation in the bovine ovary. Female fetuses at different gestational ages (60, 75, 90, 120, 150 and 210 days) were used for immunolocalization of AGTR2. At day 60, AGTR2 was localized to the cytoplasm of oogonia; from days 75 to 150, during follicle formation and development to secondary stage, AGTR2 immunostaining was weak and irregular, but from day 210 staining became evident in granulosa cells of preantral follicles and in both granulosa and theca cells of small antral follicles. These data differ from those in pigs, in which AGTR2 protein is detected in preantral follicles throughout gestation. Abundance of AGTR2 mRNA in whole ovaries did not change with fetal age. In conclusion, AGTR2 protein is expressed in ovigerous cords in fetal bovine ovaries but not in preantal follicles until the formation of antral follicles. These data suggest important species-specific differences in the expression of AGTR2 in fetal ovaries from polyovulatory and monovulatory animals.//////////////////
Expression of angiotensin II type 1 (AT1) and angiotensin II type 2 (AT2) receptors in human granulosa-lutein (GL) cells: correlation with infertility diagnoses. Pe? et al. OBJECTIVE: To correlate angiotensin II (AngII) receptor expression by granulosa-lutein (GL) cells from gonadotropin-stimulated follicles with infertility diagnosis and IVF parameters. DESIGN: The mRNA of angiotensin receptors type 1 (AT1) and type 2 (AT2) was studied in aspirated GL cells. SETTING: University laboratory and private IVF center. PATIENT(S): Seventy-three IVF patients. INTERVENTION(S): Reverse-transcription polymerase chain reaction analysis for relative expression of AT1 and AT2 receptor mRNA in women with no ovarian factor (NOF), poor ovarian reserve (PR), endometriosis (ENDO), and polycystic ovary syndrome (PCOS). MAIN OUTCOME MEASURE(S): Expression of AT1 and AT2 receptor mRNA. RESULT(S): There was a constant approximately 7:1 ratio between AT1 and AT2 receptors and a negative correlation between the AT1/AT2 ratio and patient age. There were statistically significant differences in AngII receptors in individual conditions: NOF showed a correlation between AT1 and AT2 receptors and a negative correlation between AT1 receptor expression, embryo fragmentation and number of metaphase II (MII) oocytes; PR showed a negative correlation between AT2 receptor expression and number of MII oocytes; PCOS AT1 receptor expression correlated negatively with the units of FSH administered and with patients' age; ENDO showed no significant correlations. CONCLUSION(S): Mural GL cells express AT1 receptor much more than AT2 receptor. AngII receptor expression varies with age and infertility diagnosis. Low expression of AngII receptors was associated with high-dose stimulation in women with PR. Embryo fragmentation in NOF is associated with decreased AT1 receptor expression, supporting a role for AngII in GL cell apoptosis.
Obermuller et al. (1998) analyzed ovaries from sexually mature, untreated rats by nonradioactive in situ hybridzation using an angiotensin II receptor subtype 2 (AT2)-specific anti-sense RNA probe and showed that AT2 mRNA expression could be demonstrated exclusively in follicular granulosa cells. Follicles containing AT2 mRNA-positve granulosa cells were mainly in the advanced tertiary stage of follicular development, already exhibiting features of atresia. In addition, individual collapsed, definitive atretic follicles also showed strong AT2 mRNA expression solely in granulosa cells. In corpora lutea and in other structures of the ovary, no message for the AT2 receptor could be detected. Using the Ang II receptor subtype-selective nonpeptide antagonists, DuP 753 {selective for the type 1 Ang II (AT1) receptor} and PD 123319 {selective for the type 2 Ang II (AT2) receptor}, Pucell et al. (1988) showed that follicular granulosa cells, in vivo and in vitro, exclusively express the AT2 receptor.
Follicle stages
Antral
Comment
Autoradiograms of 125I-labeled Sar1,Ile8, angiotensin II binding to ovarian sections indicated that the angiotensin II receptor binding sites were localized exclusively to a subpopulation of follicles, occurring on the granulosa and theca interna cells. Other follicles were devoid of 125I-labeled Sar1,Ile8-angiotensin II binding sites (Husain et al., 1987) .
Rainey et al. (1993) reported that no specific binding of 125I-labeled Ang II was observed using human luteinized GCs in culture. Angiotensin II did not alter the formation of 3H inositol phosphates, nor did it alter the release of P from freshly isolated cells or cells that had been in culture for 5 days. Angiotensin II was also unable to alter basal or gonadotropin-stimulated cAMP production. These data suggest that human luteinized GCs exhibit little or no type 1 or type 2 AngII receptors.
Phenotypes
Mutations
1 mutations
Species: mouse
Mutation name: None
type: null mutation fertility: fertile Comment:Hein et al. (1995) and Ichiki et al. (1995) independently generated mice lacking the gene encoding the angiotensin II type 2 receptor (which they symbolized AT2). Hein et al. (1995) found that mutant mice develop normally but have an impaired drinking response to water deprivation as well as a reduction in spontaneous movements. Their baseline blood pressure was normal, but they showed an increased vasopressor response to injection of angiotensin II.