Cyclical secretion of prorenin during the menstrual cycle: synchronization with luteinizing hormone and progesterone

Retinal Vascular Changes during the Menstrual Cycle Detected with Optical Coherence Tomography Angiography

Purpose

To evaluate the effects of the menstrual cycle on the retinal vascular status of healthy women by optical coherence tomography angiography (OCTA).

Materials and Methods

Healthy women with regular natural menstrual cycles of 28 to 30 days were recruited for this prospective study. The women's retinal vascular status was measured by OCTA at 3 time points: the early follicular, ovulatory, and midluteal phases of the menstrual cycle. The main outcome measures were foveal avascular zone (FAZ) parameters, perfusion density (PD) percentage in the superficial retinal capillary plexus (SCP), and PD percentage in the deep retinal capillary plexus (DCP). The mean arterial pressure (MAP), spherical equivalent (SE), best-corrected visual acuity (BCVA), intraocular pressure (IOP), and axial (AL) were also measured in a same menstrual cycle.

Results

In total, 62 right eyes of 62 women were included in the study. The mean age was 27.0 ± 1.73 (range, 24 to 31) years, and the mean menstrual cycle was 28.90 ± 0.84 (range, 28 to 30) days. The mean values of the DCP-PD parameters were significantly decreased in the nasal and inferior ETDRS subfields during the ovulatory phase. The mean DCP-PD in the nasal ETDRS subfield in the early follicular, ovulatory, and luteal phases was 54.11 ± 2.85, 56.39 ± 3.03, and 55.70 ± 3.27, respectively. The mean DCP-PD in the inferior ETDRS subfield in the early follicular, ovulatory, and midluteal phases was 52.90 ± 3.30, 54.86 ± 2.51, and 55.21 ± 2.64, respectively. No significant differences were found in MAP, SE, AL, IOP, FAZ area, or other quadrants of PD parameters, and no significant correlation was found between parameters by OCTA and age, MAP,SE, axial length, or IOP.

Conclusions

The DCP-PD decreased in the nasal and inferior ETDRS subfields during the ovulatory phase in our study. This may indicate the need to consider the menstrual phase when interpreting DCP-PD parameters by OCTA in healthy women.

Determinants of Maternal Renin-Angiotensin-Aldosterone-System Activation in Early Pregnancy: Insights From 2 Cohorts

CONTEXT

The corpus luteum (CL) secretes prorenin, renin's inactive precursor. It may thus contribute to the renin-angiotensin-aldosterone-system (RAAS) activation that is required for maternal adaptation in pregnancy. Whether this activation is disturbed in pregnancies lacking a CL is unknown.

OBJECTIVE

The objective of this work is to investigate maternal RAAS determinants in early pregnancy.

DESIGN AND SETTING

Two observational prospective cohort studies.

TOOK PLACE AT

2 tertiary referral hospitals.

PATIENTS AND INTERVENTION(S)

Pregnancies (n = 277) were stratified by CL number and in vitro fertilization (IVF) protocol: 0 CL (programmed cycle frozen embryo transfer [FET], n = 28), 1 CL (natural cycle FET, n = 41 and spontaneous conceptions, n = 139), and more than 1 CL (ovarian stimulation and fresh embryo transfer, n = 69).

METHODS

Quantification was performed for maternal prorenin, renin, and aldosterone blood levels at 5, 9, and 11 weeks of gestation.

RESULTS

Prorenin and renin were lower in the absence of a CL at all time points when compared to 1 CL, whereas prorenin, renin, and aldosterone were higher in the presence of more than 1 CL vs 1 CL (P < .05). Ovarian stimulation with menopausal gonadotropin resulted in higher prorenin, renin, and aldosterone concentrations during the late first trimester than recombinant follicle-stimulating hormone (P < .05). Prorenin, and to a lesser degree renin, correlated positively with serum progesterone and relaxin, but not serum estradiol. Total follicle diameter, body mass index (BMI), polycystic ovary syndrome (PCOS), and antimüllerian hormone (AMH) were additional determinants of circulating prorenin. Finally, pregnancies conceived in the absence of a CL were more disposed to develop preeclampsia.

CONCLUSIONS

CL number, IVF protocol, BMI, PCOS, and AMH affect maternal RAAS activation in early pregnancy, and may thus contribute to pregnancy complications.

Independent serum markers of corpora lutea function after gonadotropin-releasing hormone agonist trigger and adjuvant low dose human chorionic gonadotropin in in vitro fertilization

OBJECTIVE

To characterize corpora lutea (CL) function after gonadotropin-releasing hormone agonist (GnRHa) trigger with the use of adjuvant human chorionic gonadotropin (hCG).

DESIGN

Secondary analysis of serum from prospective randomized clinical trial.

SETTING

University-based fertility center.

PATIENT(S)

Women under 40 years of age at risk of ovarian hyperstimulation syndrome (OHSS) with serum E₂ level <4,000 pg/mL.

INTERVENTIONS(S)

All subjects underwent ovarian stimulation with the use of a GnRH antagonist protocol. Within a larger study, subjects were randomized to receive 1,000 IU hCG at the time of GnRHa trigger and placebo at the time of vaginal oocyte retrieval (VOR) or placebo at the time of GnRHa trigger and 1,500 IU hCG at the time of VOR.

MAIN OUTCOME MEASURE(S)

Luteal phase and early pregnancy curves of serum prorenin and 17α-hydroxyprogesterone (17OH-P).

RESULT(S)

Thirty subjects enrolled in this secondary analysis. Serum 17OH-P peaked in the early luteal phase, 5 days after GnRHa trigger, with a nadir in the mid-luteal phase 9 days after trigger. Serum prorenin peaked in the luteal phase 2 days after GnRHa trigger, independently from adjuvant hCG timing, and reached a nadir at 9 days after trigger. CL function appears higher when adjuvant hCG is given at VOR compared with adjuvant hCG given at the time of trigger.

CONCLUSION(S)

CL function, as interpreted by proxy measures of serum prorenin and 17OH-P with pregnancy, continues despite GnRHa trigger. Both options for adjuvant hCG timing are sufficient for CL rescue and successful pregnancy, so the potential for OHSS risk with increased CL activity after hCG at VOR should be considered.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01815138.

Application of non-invasive detection of peripheral vascular dysfunction in ovarian hyperstimulation syndrome (OHSS): A pilot study of clinical relevance

OBJECTIVE

The current study tested the hypothesis that vascular endothelial function, as reflected by the reactive hyperemia index (RHI), and biochemical factors, including VEGF, TNFα, CRP, inhibin A, and inhibin B, were involved in the pathogenesis of ovarian hyperstimulation syndrome (OHSS).

MATERIALS AND METHODS

This study was conducted between June 2010 and June 2012, enrolling 15 patients with OHSS and 6 healthy control subjects <45 years of age. Detailed clinical parameters were reviewed, including serum VEGF, TNFα, CRP, inhibin A, inhibin B, and hematocrit. RHI assessed by novel automatic peripheral arterial tonography was used to evaluate the vascular endothelial function.

RESULTS

Twenty-one subjects were evaluated. There was no significant difference between patients with OHSS and control subjects with respect to VEGF, TNFα, CRP, inhibin A and inhibin B. The RHI was not significantly different between patients with OHSS and control subjects (mean, 1.8 ± 0.4 vs. 1.7 ± 0.2). The hematocrit was significantly different between patients with OHSS and control subjects.

CONCLUSIONS

Our preliminary data did not reveal direct evidence of vascular endothelial dysfunction in patients with OHSS. To identify whether RHI could reflect vascular endothelial dysfunction in patients with OHSS, more cases with different severities of OHSS should be recruited in the future study.

Bovine ovarian cells have (pro)renin receptors and prorenin induces resumption of meiosis in vitro

The discovery of a receptor that binds prorenin and renin in human endothelial and mesangial cells highlights the possible effect of renin-independent prorenin in the resumption of meiosis in oocytes that was postulated in the 1980s.This study aimed to identify the (pro)renin receptor in the ovary and to assess the effect of prorenin on meiotic resumption. The (pro)renin receptor protein was detected in bovine cumulus-oocyte complexes, theca cells, granulosa cells, and in the corpus luteum. Abundant (pro)renin receptor messenger ribonucleic acid (mRNA) was detected in the oocytes and cumulus cells, while prorenin mRNA was identified in the cumulus cells only. Prorenin at concentrations of 10(-10), 10(-9), and 10(-8)M incubated with oocytes co-cultured with follicular hemisections for 15h caused the resumption of oocyte meiosis. Aliskiren, which inhibits free renin and receptor-bound renin/prorenin, at concentrations of 10(-7), 10(-5), and 10(-3)M blocked this effect (P<0.05). To determine the involvement of angiotensin II in prorenin-induced meiosis resumption, cumulus-oocyte complexes and follicular hemisections were treated with prorenin and with angiotensin II or saralasin (angiotensin II antagonist). Prorenin induced the resumption of meiosis independently of angiotensin II. Furthermore, cumulus-oocyte complexes cultured with forskolin (200μM) and treated with prorenin and aliskiren did not exhibit a prorenin-induced resumption of meiosis (P<0.05). Only the oocytes' cyclic adenosine monophosphate levels seemed to be regulated by prorenin and/or forskolin treatment after incubation for 6h. To the best of our knowledge, this is the first study to identify the (pro)renin receptor in ovarian cells and to demonstrate the independent role of prorenin in the resumption of oocyte meiosis in cattle.

Roles of the circulating renin-angiotensin-aldosterone system in human pregnancy

This review describes the changes that occur in circulating renin-angiotensin-aldosterone system (RAAS) components in human pregnancy. These changes depend on endocrine secretions from the ovary and possibly the placenta and decidua. Not only do these hormonal secretions directly contribute to the increase in RAAS levels, they also cause physiological changes within the cardiovascular system and the kidney, which, in turn, induce reflex release of renal renin. High levels of ANG II play a critical role in maintaining circulating blood volume, blood pressure, and uteroplacental blood flow through interactions with the ANG II type I receptor and through increased production of downstream peptides acting on a changing ANG receptor phenotype. The increase in ANG II early in gestation is driven by estrogen-induced increments in angiotensinogen (AGT) levels, so there cannot be negative feedback leading to reduced ANG II production. AGT can exist in various forms in terms of redox state or complexed with other proteins as polymers; these affect the ability of renin to cleave ANG I from AGT. Thus, during pregnancy the rate of ANG I production varies not only because levels of renin change in response to homeostatic demand but also because AGT changes not only in concentration but in form. Activation of the circulating and intrarenal RAASs is essential for normal pregnancy outcome subserving the increased demand for salt and, hence, water during pregnancy. Thus, the complex integration of the secretions and actions of the circulating maternal renin-angiotensin system in pregnancy plays a key role in pregnancy outcome.

The ovarian hyperstimulation syndrome

Ovarian hyperstimulation syndrome (OHSS) is an iatrogenic complication induced by exogenous administration of substances that are used to stimulate follicular growth and ovulation. There has only been one reported incidence of a spontaneous occurrence of OHSS and that was in 1992. The crucial event in the development of the syndrome is the administration of human chorionic gonadotropin (HCG), although several studies have reported the onset of OHSS after gonadotropin stimulation despite withholding HCG. OHSS is represented by a broad spectrum of clinical and laboratory manifestations which, in the severest form, can induce a life-threatening condition.

Renin and ovarian vascularization in cows with follicular cysts after epidural administration of a GnRH analogue

The ovarian renin-angiotensin system may play an important role in follicular growth and maturation, as well as in the process of ovulation. The aim of this study was to investigate the effects of administration of a GnRH analogue to cows with ovarian follicular cysts on plasma renin concentrations and ovarian vascularization. This study was performed with 60 Friesian cows, which were diagnosed with follicular cysts, and randomly allocated into two groups: group A (treatment; n=30) received 2ml of lecirelin (Dalmarelin((R)) - Fatro), per head via sacro-coccygeal epidural, and group B (control; n=30) received 2ml saline solution (0.9% NaCl) per head by the same route. Blood samples were immediately collected prior to administration (T0) and then 24h (T1), 48h (T2) and 8 days (T3) after administration of the treatment, for both groups. Ovarian vascularization was evaluated utilizing Power Doppler on these same days in 10 animals from each group. The number of pixels detected by Power Doppler was used as an indicator of the degree of vascularization. Plasma renin concentrations remained relatively constant for the control (group B) animals, but increased as the sampling period progressed (NS) for the treated cows (group A). Similarly, there were no changes in ovarian vascularization (number of pixels) for the control cows, but vascularization increased throughout the sampling period in the treated animals. The number of pixels associated with cysts was significantly higher for treated compared to control cows at 24h after treatment (P<0.001). The epidural administration of a GnRH analogue was determined to be a highly effective therapy for follicular cysts (regression occurred in 82% of treated cows within 8+/-2 days after treatment, but in none of the control cows), which also enhanced ovarian vascularization.

Novel Drugs Targeting Hypertension: Renin Inhibitors

The first renin inhibitor, aliskiren, will soon enter the clinical arena. This review summarizes the potential differences between renin inhibitors and the currently existing blockers of the renin-angiotensin system (RAS) [ie, the ACE inhibitors and the angiotensin II type 1 (AT(1)) receptor antagonists], taking also into consideration the recently discovered (pro)renin receptor. This receptor not only activates the inactive precursor of renin, prorenin, but it also exerts direct renin/prorenin-induced effects, independently of angiotensin. The review ends with a brief overview of the available (pre)clinical aliskiren data and a description of its safety profile.

Localized accumulation of angiotensin II and production of angiotensin-(1-7) in rat luteal cells and effects on steroidogenesis

These studies aim to investigate subcellular distribution of angiotensin II (ANG II) in rat luteal cells, identify other bioactive angiotensin peptides, and investigate a role for angiotensin peptides in luteal steroidogenesis. Confocal microscopy showed ANG II distributed within the cytoplasm and nuclei of luteal cells. HPLC analysis showed peaks that eluted with the same retention times as ANG-(1-7), ANG II, and ANG III. Their relative concentrations were ANG II >or= ANG-(1-7) > ANG III, and accumulation was modulated by quinapril, an inhibitor of angiotensin-converting enzyme (ACE), Z-proprolinal (ZPP), an inhibitor of prolyl endopeptidase (PEP), and parachloromercurylsulfonic acid (PCMS), an inhibitor of sulfhydryl protease. Phenylmethylsulfonyl fluoride (PMSF), a serine protease inhibitor, did not affect peptide accumulation. Quinapril, ZPP, PCMS, and PMSF, as well as losartan and PD-123319, the angiotensin receptor type 1 (AT1) and type 2 (AT2) receptor antagonists, were used in progesterone production studies. ZPP significantly reduced luteinizing hormone (LH)-dependent progesterone production (P < 0.05). Quinapril plus ZPP had a greater inhibitory effect on LH-stimulated progesterone than either inhibitor alone, but this was not reversed by exogenous ANG II or ANG-(1-7). Both PCMS and PMSF acutely blocked LH-stimulated progesterone, and PCMS blocked LH-sensitive cAMP accumulation. Losartan inhibited progesterone production in permeabilized but not intact luteal cells and was reversed by ANG II. PD-123319 had no significant effect on luteal progesterone production in either intact or permeabilized cells. These data suggest that steroidogenesis may be modulated by angiotensin peptides that act in part through intracellular AT1 receptors.

Effect of angiotensin-converting enzyme-inhibiting therapy on the expression of vascular endothelial growth factor in hyperstimulated rat ovary

OBJECTIVE

To determine the effect of angiotensin-converting enzyme-inhibiting therapy on the expression of vascular endothelial growth factor (VEGF) in the hyperstimulated rat ovary.

DESIGN

Experimental study.

SETTING

University animal research laboratory.

ANIMAL(S)

Thirty Wistar albino adult female rats were studied; 20 rats were stimulated with gonadotropins (groups 1 and 2), and 10 were controls (group 3). Ten of the stimulated rats received additional treatment with enalapril (group 2).

INTERVENTION(S)

At the end of the treatment period, rat ovaries were subjected to immunohistochemical staining with anti-VEGF antibodies.

MAIN OUTCOME MEASURE(S)

VEGF staining intensity was graded semiquantitatively, and the H-score was calculated by light microscopic examination of the groups.

RESULT(S)

VEGF expression was found to be significantly higher in the endothelium and stroma in groups 1 and 2 compared with group 3. Although VEGF immunoreactivity was lower in the stimulation regimen plus enalapril group compared with the stimulation regimen-only group, the difference was insignificant.

CONCLUSION(S)

Enalapril does not seem to have a significant effect on VEGF expression in the hyperstimulated rat ovary. Because angiotensin II exerts its multiple actions via specific receptors, there may be other factors, such as a receptor blockade, that contribute to the VEGF expression.

Follicular fluid renin concentration in patients with polycystic ovaries treated with gonadotrophins in an in vitro fertilisation programme

The initial hypothesis was that the follicular fluid prorenin concentration was higher in women with polycystic ovaries (PCO) compared to normally cycling women stimulated by gonadotrophins. In a controlled prospective study, 47 women undergoing in vitro fertilisation (IVF) were enrolled: 20 women with PCO represented the study group and 27 normally cycling women the control group. Plasma prorenin, active renin, serum oestradiol, and androstenedione concentrations were measured on the day of human chorionic gonadotrophin (HCG) administration and 36 hours after HCG administration. Follicular fluid prorenin, active renin, oestradiol, and androstenedione concentrations from the dominant follicle and pooled follicles were measured 36 hours after HCG administration. Plasma prorenin concentration 36 hours after HCG administration was significantly higher in the PCO group (1867 microU/l; range 1137-3162 microU/l) than in controls (860 microU/l; range 433-1763 microU/l) (p = 0.007). The follicular fluid prorenin concentration in the dominant follicle and in the pooled follicles was lower in the PCO group (20190 microU/l; range 11130-25955 microU/l) than in controls (46930 microU/l; range 20671-66171 microU/l) (p = 0.003). We conclude that plasma prorenin concentrations in gonadotrophin-stimulated PCO cycles are augmented due to numerous follicles. Lower follicular fluid prorenin concentrations in women with PCO show that the synthesis of prorenin in theca cells starts later after HCG administration than in normally cycling women.

Serum total renin after tubal sterilization

The effect of laparoscopic tubal sterilization by Hulka or Filshie clips on serum total renin levels was evaluated in 33 healthy, regularly menstruating women. Serum total renin levels were measured in the follicular (days 3 to 7) and in the luteal (days 20 to 24) phase during the cycle immediately preceeding the sterilization and 12 months after the procedure. The total renin secreted did not change after the sterilization. The follicular phase levels were lower (160 +/- 113 and 170 +/- 93 ng/l, respectively) than luteal phase levels (230 +/- 124 and 228 +/- 83 ng/l, respectively) in both cycles studied (p=0.0001 for both). The length of the menstrual cycle was not affected, either. Laparoscopic tubal sterilization caused no measurable changes in total renin secretion during one year follow-up.

Periovulatory changes in the local release of vasoactive peptides, prostaglandin f(2alpha), and steroid hormones from bovine mature follicles in vivo

We previously proposed that an endothelin-angiotensin-atrial natriuretic peptide system may contribute to inducing ovulation of mature bovine follicles by modulating follicular secretion of steroids and prostaglandins (PGs). Thus, this study aimed to determine the real-time changes in the local release of angiotensin II (Ang II), endothelin (ET), atrial natriuretic peptide (ANP), PGF(2alpha), and steroid hormones from bovine mature follicles during the periovulatory period in vivo. Seven cows were treated for superovulation using FSH and PGF(2alpha) injections. Two dialysis capillary membranes per follicle were surgically implanted into the theca layer of mature follicles and connected to a microdialysis system (MDS). Fractions of the perfusate were collected from Day -1 (Day 0 = LH surge) to Day 3. Five out of seven treated cows were normally ovulated, and the newly formed corpora lutea were observed at the end of the experiment. In these five ovulated cows, the release of estradiol, androstenedione, and progesterone in the theca layer increased (P < 0.05) synchronously with the LH surge. Acute increases in PGF(2alpha) and Ang II concentrations in the ovarian venous plasma (OVP) were observed at 24-48 h after the peak of the LH surge, when multiple ovulations were expected to occur. The follicular Ang II release was low during the pre-LH surge period and rose (P < 0.05) at the beginning of the increase in the LH surge. On the other hand, ET-1 release dropped (P < 0.05) when plasma LH started to increase. However, no clear changes in ANP concentration in the MDS perfusate and plasma were observed. The above local changes in Ang II, PGF(2alpha), as well as steroid hormones were not observed in cows (n = 2) that did not show an LH surge and ovulation. The present results demonstrate for the first time the local release of Ang II, ET-1, and ANP from the bovine mature follicle in real-time in vivo and show that Ang II and PGF(2alpha) concentrations in the OVP acutely increase around the time of ovulation. The overall results support the concept of a local functional ET-Ang-ANP system in the bovine mature follicle that may be involved in the ovulatory process.

High plasma prorenin in non diabetic siblings of non insulin-dependent diabetes mellitus patients

In a large cohort (no. = 361) of NIDDM probands and their concordant/discordant siblings from no. = 132 families we studied: 1. the levels of plasma prorenin in non affected siblings of NIDDM probands as opposed to normal subjects without family history of diabetes, and 2. whether plasma prorenin raises in parallel to urinary protein loss in NIDDM patients. Prorenin (solid-phase trypsin) and micro-macroalbuminuria (radioimmunoassay) were evaluated. Plasma prorenin was higher in NIDDM probands and siblings than in non NIDDM siblings (37+/-31 vs. 25+/-15 ng/ml/h, p<0.0005) who, in turn, showed higher plasma prorenin than non diabetic controls without family history of diabetes (25+/-15 vs. 17+/-8 ng/ml/h, p<0.005). Plasma prorenin was higher in NIDDM siblings of micro-macroalbuminuric probands than in NIDDM siblings of non micro-macroalbuminuric probands (40+/-26 vs. 29+/-20 ng/ml/h, mean +/- SD, p = 0.0058) whereas no difference was found among non diabetic siblings (24+/-14 vs. 22+/-11 ng/ml/h, NS). Our data confirm that plasma prorenin is elevated in NIDDM patients, and show: 1. that the raise of plasma prorenin in non-NIDDM siblings of a diabetic patient does not depend entirely from the presence of diabetes, and 2. that plasma prorenin in NIDDM probands and their concordant siblings goes along with micro-macroalbuminuria.

Gonadotropins induce higher active renin levels in the follicular fluid of normal and hyperstimulated cycles

The objective of this study was to analyze follicular fluid active renin and its relationship to steroid hormones throughout the normal and gonadotropin-stimulated menstrual cycle. Active renin was measured in the follicular fluid of patients undergoing tubal sterilization (n = 16) and in vitro fertilization (IVF) (n = 25); IVF patients were either in a natural cycle (n = 7) or undergoing controlled ovarian hyperstimulation (n = 18). The largest visible follicle was aspirated at the time of laparoscopic tubal sterilization; ultrasound guided transvaginal follicular aspiration was used in the IVF group. Follicular fluid active renin, estradiol and progesterone levels were measured with immunoradiometric and fluoroimmunoassays. The cycle day was correlated with the spontaneous luteinizing hormone (LH) surge or human chorionic gonadotropin (hCG) administration, as well as active renin, estradiol, progesterone levels and the estradiol/progesterone ratio using simple and multiple regression and analysis of variance (ANOVA). Cycle day independently influenced active renin, progesterone and the estradiol/progesterone ratio in a statistically significant manner (p < 0.0001). The active renin and progesterone levels were highest during the periovulatory period (p < 0.0001 and p < 0.002, respectively) and the estradiol/progesterone ratio correlated inversely with cycle day (p < 0.003). Although the follicular fluid active renin, estradiol and progesterone levels were higher after controlled ovarian hyperstimulation when compared to natural cycles, this difference did not reach statistical significance. Our findings suggest that active renin levels in follicular fluid increase in the follicular phase of the menstrual cycle, reaching peak levels in the periovulatory period following the LH surge or hCG administration, providing indirect support for the hypothesis that the ovarian renin-angiotensin system (RAS) is under gonadotropin control.

Determinants of interindividual variation of renin and prorenin concentrations: evidence for a sexual dimorphism of (pro)renin levels in humans

BACKGROUND

Plasma renin concentrations are an important factor in cardiovascular risk profiling.

OBJECTIVE

To investigate the effects of sex, medication, and anthropometric factors that may contribute to the interindividual variation in the plasma concentrations of renin and its precursor prorenin.

DESIGN AND METHODS

Prorenin and renin levels in 327 men and 383 women, aged 52-69 years, who participated in a 1994 reexamination of a previous population survey in Bavaria, were measured by immunoradiometric assay.

RESULTS

Prorenin and renin levels in men were significantly higher than those in women, those in women without estrogen replacement therapy were significantly higher than those in women with estrogen replacement therapy, and those in diabetics were significantly higher than those in nondiabetics. Prorenin level was correlated negatively to blood pressure and positively to age and the use of diuretics; it was normal in subjects using angiotensin converting enzyme inhibitors and beta-adrenergic antagonists (beta-blockers). Renin level was correlated negatively to atrial natriuretic peptide level and the use of beta-blockers, and it was elevated above normal levels in subjects using angiotensin converting enzyme inhibitors and diuretics as well as in subjects who had previously suffered myocardial infarction. After exclusion of data for women being administered estrogen replacement therapy, multivariate analysis revealed that sex (P<0.001), age (P<0.02), blood pressure (P<0.002), diabetes (P<0.05), and the use of angiotensin converting enzyme inhibitors (P<0.002), beta-blockers (P<0.001), and diuretics (P<0.05) were independent determinants of plasma prorenin. Plasma renin was independently related to atrial natriuretic peptide level (P<0.01) and the use of angiotensin converting enzyme inhibitors (P<0.001), beta-blockers (P<0.001), and diuretics (P<0.05).

CONCLUSIONS

These data demonstrate that there is a sexual dimorphism of prorenin levels in humans, suggesting that sex hormones affect the regulation of the renin gene. Data confirm previous reports of elevated prorenin levels in diabetics and older subjects, as well as of lower than normal prorenin levels in subjects with hypertension in smaller populations. Our findings may help to clarify the potential (patho)physiologic functions of prorenin and to identify the factors that influence the constitutive secretion and intracellular processing of this prohormone.

The ovarian renin-angiotensin system in reproductive physiology

The identification of the presence of prorenin, renin, angiotensinogen, angiotensin-converting enzyme, angiotensin II (Ang II), and Ang II receptors in the ovary suggests that there is a functional ovarian renin-angiotensin system (RAS). It could play a significant role in such areas of ovarian physiology as follicular development, steroidogenesis, oocyte maturation, ovulation, and follicle atresia. Expression of the ovarian RAS is regulated by gonadotropins. Ang II, a bioactive octapeptide of RAS, has important effects as a paracrine/autocrine regulator at different stages of the reproductive cycle. Ang II modulates ovarian steroidogenesis and formation of the corpus luteum and also stimulates oocyte maturation and ovulation via Ang II receptors on granulosa cells. In addition, increasing evidence demonstrates that Ang II is a major factor in regulating the function of atretic follicles. In any physiologic system, aberrations result in the development of pathologic states. Disturbances in the ovarian RAS can be the cause or the result of such reproductive disorders as polycystic ovary syndrome, ovarian hyperstimulation syndrome, ovarian tumors, and ectopic pregnancy. Data support the concept of an active and regulated RAS in ovarian follicles. Species differences observed in the expression of ovarian RAS suggest varying functional roles among species with respect to ovarian physiology.

The effect of microtubule-disrupting drugs on morphology, progesterone and prorenin secretion of bovine cultured ovarian theca cells

The effect of three microtubule-disrupting drugs (vinblastine, colchicine and nocodazole) on basal and LH-stimulated secretion of progesterone and prorenin by bovine theca cells was studied. Microtubules were visualized immunocytochemically using a monoclonal antibody against the alpha-subunit of tubulin and a secondary antibody conjugated with rhodamine. Progesterone and prorenin secretion were detected by adequate radioimmunoassays. Theca cells treated with LH alone or with a combination of LH, colchicine and vinblastine, showed round shape and disorganization of microtubules which were more obvious than after treatment with the two disrupting drugs alone. Nocodazole or LH treatment alone resulted in the formation of numerous cell processes, conspicuously different in shape from those in the controls. All three drugs increased basal progesterone secretion independently on the dose, but were without effect on basal prorenin secretion. LH-stimulated progesterone secretion was significantly suppressed by each of the three drugs while LH-stimulated prorenin secretion was decreased only by high doses of vinblastine and nocodazole. Colchicine in all three doses used did not exert any significant effect. The results obtained suggest that microtubules are involved in progesterone but not in prorenin secretion.

Characteristics and treatment of hypertension in women: a review of the literature

Although there are documented differences between women and men in frequency and severity of hypertension and in the relation between hypertension and cardiovascular risk, few studies have been designed to evaluate efficacy and safety of antihypertensive therapy in women. Efficacy of nonpharmacologic interventions to lower blood pressure may differ between the sexes; women have greater difficulty losing weight than men but may respond better than men to dietary sodium reduction. In general, women and men do not respond differently to antihypertensive therapy; however, there may be differences in response to certain classes of antihypertensives. There are limited data on safety of specific antihypertensive agents in women. In some studies, researchers found a greater incidence of adverse effects in women. Effects on sexual functioning and pharmacokinetic and pharmacodynamic characteristics of antihypertensive drugs in women have been studies inadequately. More data are needed to guide the management of hypertension in women.

Prorenin is elevated in polycystic ovary syndrome and may reflect hyperandrogenism

OBJECTIVE

To examine the null hypothesis that women with polycystic ovary syndrome (PCOS) produce similar levels of prorenin and other components of the ovarian-derived prorenin to angiotensin cascade (ODPAC) at baseline and after stimulation with clomiphene citrate (CC) or hMG when compared with normal age- and weight-matched ovulatory controls.

DESIGN

Prospective controlled clinical trial.

SETTING

Infertility clinic in a university-based county hospital and a hospital-based private infertility practice.

PATIENTS

Twenty-eight infertile women aged 18 to 35 years. Thirteen patients were diagnosed with PCOS. Fifteen normal ovulatory patients who were matched for age and weight served as controls.

INTERVENTIONS

Twenty patients were stimulated with CC and eight were stimulated with hMG.

MAIN OUTCOME MEASURES

Serum E2, P, T, androstenedione (A), DHEAS, LH, FSH, and plasma prorenin, active renin, and angiotensin II (Ang II) were measured at baseline and during the preovulatory and midluteal phases of the stimulation cycles.

RESULTS

Baseline plasma prorenin in PCOS was higher than that of follicular phase controls. Plasma prorenin correlated significantly with peripheral androgen levels. Prorenin, active renin, and Ang II increased in response to gonadotropins with the largest increases occurring in control patients receiving CC. An association was seen between ovulation with CC and lower baseline levels of active renin.

CONCLUSIONS

The null hypothesis was rejected. Infertile women with PCOS have higher baseline prorenin levels when compared with age- and weight-matched ovulatory controls. There is a significant correlation between prorenin and the peripheral levels of androgens produced during ovarian stimulation. Baseline active renin levels may be predictive of ovulation with CC.

Ovulation as a tissue remodelling process. Proteolysis and cumulus expansion

Ovulation, recurring every midcycle of the mammalian female and triggered by a surge of luteinizing hormone (LH) released from the pituitary, is an essential prerequisite for fertilization and subsequent embryonic development. Here we shall describe two of the biological components of the ovulatory response, cumulus expansion (frequently denoted as cumulus maturation) and the rupture of follicular wall, both crucial for the release of a fertilizable ovum. The role of a proteolytic cascade and its regulation by eicosanoids will be emphasized in relation to follicle rupture. The new data implicating cumulus maturation as an essential step for the release of the ovum and the apparent mediatory role of interleukin-1 in this process will be presented. LH/hCG stimulates, in the preovulatory follicles, a cascade of proteolytic enzymes, including plasminogen activator (PA), plasmin and matrix metalloproteinase 1 (MMP-1). These enzymes bring about the degradation of perifollicular matrix and, most notably, the decomposition of the meshwork of collagen fibers which provides the strength to follicular wall. Furthermore, pharmacological blockage of any of these enzymes resulted in inhibition of follicle rupture. LH/hCG stimulates, in addition, an increase in ovarian production of eicosanoids. These include prostaglandins, obtained from arachidonic acid via the cyclooxygenase pathway and leukotrienes, the products of lipoxygenase. Previous studies from our and other laboratories have demonstrated the ability of inhibitors of cyclooxygenase and of lipoxygenases to suppress ovulation in several mammalian species. MK-886, which inhibits the translocation of 5-lipoxygenase (5-LO) from the cytosol and its binding to the membranal 5-LO activating enzyme, suppressed dose-dependently follicular rupture from the treated ovary. Zymographic analysis of ovarian extracts from PMSG/hCG-stimulated rats revealed a band of collagenolytic activity at 52kD, corresponding to human MMP-1 and at 72kD, corresponding to human MMP-2. Both activities were markedly stimulated by administration of hCG and were significantly inhibited by indomethacin, NDGA or MK-886. Thus, eicosanoids seem to mediate LH stimulation of follicular collagenase. Interleukin-1 (IL-1) has been recently implicated in ovulation. The ability of an IL-1 receptor antagonist (ra) to block ovulation in vivo and in vitro has been demonstrated recently. Morphological examination of the ovulatory follicles failing to ovulate suggests that this effect is exerted by inhibiting cumulus oophorus expansion and detachment from mural granulosa cells. In vitro, IL-1ra attenuated the action of hCG and FSH on cumulus expansion and follicular hyaluronic acid synthesis. Thus, IL-1 seems to mediate and/or facilitate gonadotropin action on cumulus expansion, and hence on ovulation.

Ovarian derived prorenin-angiotensin cascade in human reproduction

OBJECTIVE

To review the available literature concerning the renin-angiotensin system of the human and animal ovary and to outline the clinical relevance of this system.

DESIGN

The location, function, and regulation of the components of the ovarian prorenin cascade are described. The possible functions of this system as well as its association with common gynecologic problems are also given.

CONCLUSIONS

The ovary contains a complete cascade whose end product is the formation of angiotensin II. Angiotensin II may have a role in steroid synthesis, oocyte maturation, ovulation, and corpus luteum formation. Further, aberrations in this system are associated with ovarian tumors, ectopic pregnancy, pre-eclampsia, and ovarian hyperstimulation syndrome.

Prorenin and active renin concentrations in ovarian follicular fluid increase after the LH peak in superovulated heifers

1. The aim was to analyse the in vivo variations with time of prorenin and active renin and their relationship to steroid hormones in ovarian follicular fluid during follicular growth in heifers. 2. Thirty one beef heifers were assigned to two groups after oestrous synchronization: an unstimulated and a follicle-stimulating hormone (FSH)-treated (superovulated) group. Within each group, animals were slaughtered at different times of the follicular phase of the oestrous cycle. Ovarian follicular fluids were aspirated and analysed for the concentrations of active renin, prorenin, oestradiol-17 beta (E2) and progesterone (P4). 3. Prorenin and active renin concentrations in follicular fluid remained constant until the luteinizing hormone (LH) peak, after which time they increased four- and two-fold, respectively, in superovulated heifers. 4. In follicular fluid, prorenin and active renin correlated negatively with oestradiol and E2/P4 ratio but positively with progesterone during follicular growth in superovulated heifers. Prorenin also correlated negatively with oestradiol and E2/P4 ratio in unstimulated heifers. 5. The increase of renin concentrations in ovarian follicles after the LH peak and the correlations to steroid hormones suggest an important role of the ovarian renin-angiotensin system in bovine follicular growth and maturation.

In vitro incubation of bovine ovarian follicles: indications for an active and regulated renin-angiotensin system

1. The ovarian follicular renin-angiotensin system was investigated by using an in vitro incubation method, based on tissue incubation of individual bovine follicles. 2. Very high and varying concentrations of active renin (median 18.0 GU/kg, range 2.1-107 GU/kg; n = 101) and prorenin (11.7 GU/kg, range < 2.6-142 GU/kg; n = 101) existed in unincubated ovarian follicular tissue. 3. Active renin and prorenin increased 35 and 959%, respectively, in follicular wall tissue and incubation medium during 72 h of in vitro incubation. The protein synthesis inhibitor cyclohexamide inhibited active renin and prorenin formation. No activation of prorenin occurred in incubation medium or follicular fluid in vitro. Active renin was degraded during incubation. 4. Primarily prorenin but also active renin were secreted into the incubation medium. Secretion was directed both to the internal and external surface of the follicular wall. 5. Follicle-stimulating hormone (FSH) slightly stimulated the synthesis and secretion of prorenin in vitro. 6. The synthesis and secretion rates of active renin and prorenin varied markedly between individual follicles. 7. The finding of very high and varying concentrations of active renin in follicular wall tissues together with the formation and secretion of active renin during in vitro incubation provide further evidence for an active and regulated renin-angiotensin system in ovarian follicles.

Angiotensin II (AII) modulation of steroidogenesis by luteinized granulosa cells in vitro

PURPOSE

The purpose of the present study was to evaluate the effect of angiotensin II and its inhibitor, saralasin, on steroid production by luteinized human granulosa cells in vitro. Granulosa cells were obtained from follicular fluid aspirations from human in vitro fertilization. Cultures were established in supplemented Ham's F-10 medium. Human chorionic gonadotropin and angiotensin II were added to culture media and the effect on steroid production was measured.

RESULTS

Human chorionic gonadotropin alone stimulated production of progesterone, estradiol, and testosterone. The addition of angiotensin II resulted in a dose-dependent increase in progesterone production (428% increase compared to baseline). No effect was seen on estradiol or testosterone. However, a large increase (700%) in estradiol was seen with the addition of the competitive inhibitor of angiotensin II, saralasin.

CONCLUSION

We conclude that angiotensin II modulates progesterone production by human luteinized granulosa cells in vitro. The observed enhancement of estradiol production by angiotensin blockade suggests a tonic inhibition of estradiol secretion by endogenous angiotensin II.

Gonadotropin stimulates ovarian renin-angiotensin system in the rabbit

The present study was undertaken to assess the role of ovarian renin-angiotensin system (RAS) in the preovulatory cascade induced by gonadotropin exposure. In the in vitro perfused rabbit ovaries, exposure to human chorionic gonadotropin (hCG) enhanced the secretion rate of angiotensin II (Ang II) within 1 h. The secretion rate reached maximal levels at 6 h and then declined thereafter. The intrafollicular Ang II content and renin-like activity were also significantly increased at 2 and 4 h after exposure to hCG, compared with control ovaries perfused with medium alone. The level of intrafollicular Ang II after hCG exposure significantly exceeded the concentration of Ang II in an equivalent volume of plasma. The addition of 1 microM captopril to the perfusate significantly inhibited the secretion rate of Ang II stimulated by hCG; however, captopril affected neither the ovulatory efficiency nor prostaglandin production in ovaries treated with hCG. Captopril significantly inhibited the resumption of meiosis in the ovulated ova and follicular oocytes stimulated by hCG. The administration of 100 micrograms Ang II at 2-h intervals to the perfusate reversed the inhibitory effects of captopril on hCG-induced oocyte maturation. In conclusion, these data indicate that gonadotropin stimulates renin-like activity and Ang II production in the rabbit ovary. Ovarian renin-angiotensin system may play an important role in the process of oocyte maturation after exposure to gonadotropin.

Renin and prorenin in reproductive tissues during gestation in pigs and cattle

1. High concentrations of prorenin and active renin were previously found in ovarian follicular fluid from cattle but not from pigs. In the present study female reproductive tissues and fluids from cattle and pigs during gestation were investigated to clarify a possible species difference in active renin and prorenin concentrations. 2. Very high concentrations of active renin but no prorenin were found in corpus luteum from both species. 3. Relatively low concentrations of active renin, in the same order as in maternal blood plasma, were found in myometrium, endometrium, placenta and fetal membranes from both species. Prorenin was undetectable in these tissues except for bovine myometrium and porcine endometrium in some animals. 4. The concentrations of active renin and prorenin in amnionic fluid from both species were below the maternal plasma values. In allantoic fluid the concentrations were higher than in amnionic fluid. 5. The plasma concentrations of active renin and prorenin did not change during gestation in pigs. This finding is in contrast to the observations in humans and does not support a systemic effect of prorenin during gestation. 6. The presence of renin in the reproductive tissues, especially the very high concentrations in the corpus luteum, indicates a local function of the renin-angiotensin system during gestation.

Lewis K. Dahl Memorial Lecture. The renin system and four lines fo hypertension research. Nephron heterogeneity, the calcium connection, the prorenin vasodilator limb, and plasma renin and heart attack

As the major regulator of arterial blood pressure and sodium balance, the renin axis supports normotension or hypertension via angiotensin-mediated vasoconstriction and angiotensin plus aldosterone-induced renal sodium retention. In this endocrine servo control, renal renin is released by hypotension or salt depletion; conversely, with hypertension or volume excess, plasma renin activity falls to zero. Accordingly, any renal renin secretion is abnormal in the face of arterial hypertension. Human hypertensive disorders comprise a spectrum of abnormal vasoconstriction-volume products (renin-sodium profiles). Excess plasma renin activity for the sodium balance is created by nephron heterogeneity in which a subpopulation of ischemic nephrons hypersecretes renin and retains sodium. This excess renin impairs adaptive natriuresis of neighboring normal nephrons. Research defining the pivotal role of vascular cytosolic calcium for transducing sodium or renin-mediated vasoconstriction explains the selective value of calcium antagonists for correcting the sodium-volume-mediated, and beta-blockers or angiotensin converting enzyme inhibitors for correcting renin-mediated, arteriolar vasoconstriction. The renin precursor prorenin appears to be physiologically active, causing selective vasodilation that offsets renin-mediated vasoconstriction. Overactivity of prorenin may be involved in the hyperperfusion vascular injuries of diabetes mellitus and toxemias. Prorenin underactivity may facilitate renin-mediated ischemic vascular injury. In essential hypertension, undue plasma renin activity is powerfully and independently associated with heart attack risk. Conversely, patients with low renin activity are protected from heart attack despite higher blood pressures and greater age. Also, renin or angiotensin administration consistently causes vascular injury in the heart, brain, and kidneys of animals. These data suggest new potentials for the prevention of cardiovascular sequelae (heart attack and stroke) by using explicit strategies to curtail plasma renin activity.

Measurement and identification of prorenin and renin in ovarian follicular fluid from cattle and pig

1. In previous studies we have demonstrated and solved several methodological problems in relation to the measurement of prorenin by trypsin activation in rat, bovine, hog and horse plasma. 2. The aim of the present study was to develop a method for the measurement of prorenin in bovine and porcine ovarian follicular fluid. 3. Trypsin activation of follicular fluid generated angiotensin I immunoreactive material (AI IM) in both species. 4. The AI IM interfered with the renin assay, but could be completely removed by a cation exchange resin in a batch-wise technique. 5. The enzymatic activity of trypsin-activated prorenin and pre-existing active renin was completely inhibited by a specific inhibitor of renin. 6. The reactions were optimized and an accurate measurement of prorenin in ovarian follicular fluid was developed. 7. The existence of prorenin and renin in bovine ovarian follicular fluid was established. Prorenin and renin in porcine ovarian follicular fluid was demonstrated for the first time. 8. The ratio between ovarian follicular fluid and plasma was 43 for prorenin and 19 for active renin in cattle. The same ratios in pigs were 1.3 and 0.4, respectively. These findings indicate a species difference with respect to the amount of prorenin or active renin present in ovarian follicular fluid.

Measurement of plasma total renin by the anti-human renin monoclonal antibodies

The authors evaluated the assay performances and clinical usefulness of a newly developed solid phase radioimmunoassay (RIA) for total renin concentration (TRC) in human plasma. The direct total renin RIA was performed by a sandwich technique with a pair of anti-human renin monoclonal antibodies. Renin activation with trypsin did not change TRC. The RIA showed satisfactory assay performances and demonstrated full compatibility with a direct RIA-kit for active renin concentration (ARC) in human plasma. The values of TRC were 105.3 +/- 8.6 pg/mL in normal subjects and 136.5 +/- 14.6 pg/mL in patients with essential hypertension. The values of TRC and the ratios of ARC to TRC were high in patients with renovascular hypertension and were low in patients with primary aldosteronism. Although the TRC value in diabetic patients was 134.4 +/- 14.8 pg/mL, the ratio of ARC to TRC was low. The RIA procedure was simple since prior purification or activation of renin was not required. These results suggest that the total renin RIA and its combined use with the active renin RIA may be helpful in understanding the renin-angiotensin system in human plasma.