Angiotensin II inhibits luteinizing hormone-stimulated cholesterol side chain cleavage expression and stimulates basic fibroblast growth factor expression in bovine luteal cells in primary culture

Prorenin periconceptionally and in pregnancy: Does it have a physiological role?

Pregnancy demands major cardiovascular, renal and endocrine changes to provide an adequate blood supply for the growing fetus. The renin-angiotensin-aldosterone system plays a key role in this adaptation process. One of its components, prorenin, is released in significant amounts from the ovary and uteroplacental unit. This review describes the sources of prorenin in the periconception period and in pregnancy, including its modulation by in-vitro fertilization protocols, and discusses its potential effects, among others focusing on preeclampsia. It ends with discussing the long-term consequences, even in later life, of inappropriate renin-angiotensin-aldosterone system activity in pregnancy and offers directions for future research. Ultimately, a full understanding of the role of prorenin periconceptionally and during pregnancy will help to develop tools to diagnose and/or prevent reproductive complications.

Prorenin periconceptionally and in pregnancy: Does it have a physiological role?

Pregnancy demands major cardiovascular, renal and endocrine changes to provide an adequate blood supply for the growing fetus. The renin-angiotensin-aldosterone system plays a key role in this adaptation process. One of its components, prorenin, is released in significant amounts from the ovary and uteroplacental unit. This review describes the sources of prorenin in the periconception period and in pregnancy, including its modulation by in-vitro fertilization protocols, and discusses its potential effects, among others focusing on preeclampsia. It ends with discussing the long-term consequences, even in later life, of inappropriate renin-angiotensin-aldosterone system activity in pregnancy and offers directions for future research. Ultimately, a full understanding of the role of prorenin periconceptionally and during pregnancy will help to develop tools to diagnose and/or prevent reproductive complications.

Foxd1 is an upstream regulator of the renin-angiotensin system during metanephric kidney development

BackgroundWe tested the hypothesis that Foxd1, a transcription factor essential for normal kidney development, is an upstream regulator of the renin-angiotensin system (RAS) during ureteric bud (UB)-branching morphogenesis.MethodsUB branching, RAS gene, and protein expression were studied in embryonic mouse kidneys. RAS mRNA expression was studied in mesenchymal MK4 cells.ResultsThe number of UB tips was reduced in Foxd1^-/- compared with that in Foxd1^+/+ metanephroi on embryonic day E12.5 (14±2.1 vs. 28±1.3, P<0.05). Quantitative real-time reverse-transcription polymerase chain reaction (qRT-PCR) demonstrated that renin, angiotensin I-converting enzyme (ACE), and angiotensin (Ang) II receptor type 1 (AT₁R) mRNA levels were decreased in Foxd1^-/- compared with those in Foxd1^+/+ E14.5 metanephroi. Western blot analysis and immunohistochemistry showed decreased expression of AGT and renin proteins in Foxd1^-/- metanephroi compared with that in Foxd1^+/+ metanephroi. Foxd1 overexpression in mesenchymal MK4 cells in vitro increased renin, AGT, ACE, and AT₁R mRNA levels. Exogenous Ang II stimulated UB branching equally in whole intact E12.5 Foxd1^-/- and Foxd1^+/+ metanephroi grown ex vivo (+364±21% vs. +336±18%, P=0.42).ConclusionWe conclude that Foxd1 is an upstream positive regulator of RAS during early metanephric development and propose that the cross-talk between Foxd1 and RAS is essential in UB-branching morphogenesis.

Hypothesis: a new role for the Renin-Angiotensin system in ureteric bud branching

Branching morphogenesis in the developing mammalian kidney involves growth and branching of the ureteric bud (UB), leading to formation of its daughter collecting ducts, calyces, pelvis and ureters. Even subtle defects in the efficiency and/or accuracy of this process have profound effects on the ultimate development of the kidney and result in congenital abnormalities of the kidney and urinary tract. This review summarizes current knowledge regarding a number of genes known to regulate UB development and emphasizes an emerging role for the renin-angiotensin system (RAS) in renal branching morphogenesis. Mutations in the genes encoding components of the RAS in mice cause renal papillary hypoplasia, hydronephrosis, and urinary concentrating defect. These findings imply that UB-derived epithelia are targets for angiotensin (ANG) II actions during metanephric kidney development. Here, it is proposed that papillary hypoplasia in RAS-deficient mice is secondary to an intrinsic defect in the development of the renal medulla. This hypothesis is based on the following observations: (a) UB and surrounding stroma express angiotensinogen (AGT) and ANG II AT(1) receptors in vivo; (b) ANG II stimulates UB cell process extension, branching and cord formation in collagen gel cultures in vitro; and (c) AT(1) blockade inhibits ANG II-induced UB cell branching. It is further postulated that ANG II is a novel stroma-derived factor involved in stroma/UB cross-talk which regulates UB branching morphogenesis.

Vascular and immune regulation of corpus luteum development, maintenance, and regression in the cow

The bovine corpus luteum (CL) is a unique, transient organ with well-coordinated mechanisms by which its development, maintenance, and regression are effectively controlled. Angiogenic factors, such as vascular endothelial growth factor A and basic fibroblast growth factor, play an essential role in promoting progesterone secretion, cell proliferation, and angiogenesis. These processes are critically regulated, through both angiogenic and immune systems, by the specific immune cells, including macrophages, eosinophils, and neutrophils, that are recruited into the developing CL. The bovine luteolytic cascade appears to be similar to that of general acute inflammation in terms of time-dependent infiltration by immune cells (neutrophils, macrophages, and T lymphocytes) and drastic changes in vascular tonus and blood flow, which are regulated by luteal nitric oxide and the vasoconstrictive factors endothelin-1 and angiotensin II. Over the period of maternal recognition of pregnancy, the maternal immune system should be well controlled to accept the semiallograft fetus. The information on the presence of the developing embryo in the genital tract is suggested to be transmitted to the ovary by both the endocrine system and the circulating immune cells. In the bovine CL, the lymphatic system, but not the blood vascular system, is reconstituted during early pregnancy, and interferon tau from the embryo could trigger this novel phenomenon. Collectively, the angiogenic and vasoactive factors produced by luteal cells and the time-dependently recruited immune cells within the CL and their interactions appear to play critical roles in regulating luteal functions throughout the life span of the CL.

Prostaglandin F2alpha differentially affects mRNA expression relating to angiogenesis, vasoactivation and prostaglandins in the early and mid corpus luteum in the cow

Administration of prostaglandin (PG) F(2alpha) in cattle during the mid-luteal phase (Days 8-12 of the estrous cycle) drastically reduces the plasma progesterone concentrations and the volume of the corpus luteum (CL). However, PGF(2alpha) does not induce luteolysis during the early luteal phase (up to Day 5 of the estrous cycle). To characterize the possible distinct difference in acute response to a luteolytic dose of PGF(2alpha) administration, we determined various mRNA expressions in the early and mid CL relating to angiogenesis, vasoactivation and PG-related factors at 30 min after PGF(2alpha) injection in cyclic cows. The experiments were conducted on Day 4 (early CL) and Days 10-12 (mid CL). Cows were either injected with 500 microg PGF(2alpha) analogue or saline as the control (early CL control, n=5; early CL PGF(2alpha) treated, n=5; mid CL control, n=5; mid CL PGF(2alpha) treated, n=7). Thirty min after injection of PGF(2alpha) or saline, the cows were ovariectomized transvaginally, and the CL tissues were collected from regions designated as the periphery and center of the CL. Administration of PGF(2alpha) up-regulated the mRNA expressions of angiogenic-related factors such as vascular endothelial growth factors, vasohibin, fibroblast growth factor 2 and insulin-like growth factor-II in the early CL, whereas PGF(2alpha) down-regulated these mRNA expressions in the mid CL. In the vasoactive factors, PGF(2alpha) stimulated the mRNA expressions of endothelin-1, angiotensin converting enzyme, endothelial nitric oxide synthase (NOS) and inducible NOS in the periphery area of the mid CL, but not in the early CL. However, PGF(2alpha) drastically down-regulated PGF(2alpha) receptor mRNA expression in both regions of the early and mid CL. The results indicated a clear difference in the acute action of PGF(2alpha) depending not only on the luteal phase (immature vs. mature) but also the region (periphery vs. center) within the CL at 30 min after PGF(2alpha) injection in the cow.

Peptide hormone regulation of angiogenesis

It is now apparent that regulation of blood vessel growth contributes to the classical actions of hormones on development, growth, and reproduction. Endothelial cells are ideally positioned to respond to hormones, which act in concert with locally produced chemical mediators to regulate their growth, motility, function, and survival. Hormones affect angiogenesis either directly through actions on endothelial cells or indirectly by regulating proangiogenic factors like vascular endothelial growth factor. Importantly, the local microenvironment of endothelial cells can determine the outcome of hormone action on angiogenesis. Members of the growth hormone/prolactin/placental lactogen, the renin-angiotensin, and the kallikrein-kinin systems that exert stimulatory effects on angiogenesis can acquire antiangiogenic properties after undergoing proteolytic cleavage. In view of the opposing effects of hormonal fragments and precursor molecules, the regulation of the proteases responsible for specific protein cleavage represents an efficient mechanism for balancing angiogenesis. This review presents an overview of the actions on angiogenesis of the above-mentioned peptide hormonal families and addresses how specific proteolysis alters the final outcome of these actions in the context of health and disease.

Local regulation of corpus luteum development and regression in the cow: Impact of angiogenic and vasoactive factors

The corpus luteum (CL) of the estrous cycle in the cow is a dynamic organ which has a life time of approximately 17-18 days. The main function of the CL is to secrete a large amount of progesterone (P) thereby supporting the achievement of pregnancy. As the CL matures, the steroidogenic cells establish contact with many capillaries and the matured CL is composed of many vascular endothelial cells that account for up to 50% of all CL cells. The bovine CL produces several major angiogenic and vasoactive foctors such as vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), angiopoietin-1 and -2 (ANPT-1 and -2), prostaglandin F(2alpha) (PGF(2alpha)), endothelin-1 (EDN1), angiotensin II (Ang II) and nitric oxide (NO). These factors regulate P secretion directly and/or indirectly within the CL. Moreover, different actions of PGF(2alpha) in the early cycle CL (non-luteolytic) and the mid cycle CL (luteolytic) may provide insight into the luteolysis cascade in the cow. The aim of the present review is to describe the current concepts of the local mechanisms for the cascade of development and regression of the bovine CL as regulated by luteal angiogenic and vasoactive factors.

Association between ACE gene I/D polymorphisms and hyperandrogenism in women with polycystic ovary syndrome (PCOS) and controls

Background

I/D polymorphisms of ACE are associated with the plasma ACE concentration. The ACE is associated with the angiogenesis of ovarian endothelium in vitro as well as steroidogenesis and follicular growth in cattle. Since ACE induces a high blood supply and hypersteroidogenesis in the ovary, it may be associated with polycystic ovary syndrome (PCOS) which exhibits hyperplasia, hypervascularity of the ovarian theca interna and stroma, as well as disorderd steroidogenesis. Therefore, we hypothesized that the ACE plays some roles in the human ovary. To investigate whether the ACE I/D polymorphisms are associated with the steroidogenesis disorder in PCOS and contribute to the susceptibility of PCOS in Chinese women, we designed a case-controlled association study in 582 individuals.

Methods

The ACE I/D polymorphisms were assessed in 582 reproductive-age women. Genotyping and frequency of ACE I/D polymorphisms were obtained by PCR amplification that was performed on genomic DNA isolated from blood leucocytes. Results were analyzed in respect to clinical test results.

Results

The frequencies of the D allele and the genotypic distributions (DD, ID and II) in the women with PCOS did not differ from those in controls (P = 0.458). However, there were significant differences in the concentrations of testosterone among three genotypes both in the PCOS patients and controls (P = 0.0045, P = 0.0052, respectively). Differences were also found between these groups with distinct genotypes: DD versus II and DI versus II in the PCOS patients as well as DD versus DI and DD versus II in the controls. There were significant differences in the ratio of LH/FSH among three genotypes in the patients (P = 0.01). However, there were no statistical differences in the BMI, AAM, E2 concentrations and other serum hormone concentrations among the three genotypes both in the PCOS patients and controls.

Conclusion

The ACE I/D polymorphisms were not associated with the pathogenesis of PCOS. However, the polymorphisms were associated with the steroidogenesis in the ovary. The observation indicated that the ACE I/D polymorphisms were not the key etiological factor, which in stead may be associated with the aggravated clinical manifestations of PCOS.

Renin-angiotensin system-growth factor cross-talk: a novel mechanism for ureteric bud morphogenesis

The renin-angiotensin system (RAS) plays a critical role in kidney development. Mutations in the genes encoding components of the RAS cause a spectrum of congenital abnormalities of the kidney and renal collecting system, ranging from hypoplasia of the renal medulla and hydronephrosis in mice to renal tubular dysgenesis in humans. However, the mechanisms by which an intact RAS controls proper renal system development and how aberrations in the RAS result in abnormal kidney and renal collecting system development are poorly understood. The renal collecting system originates from the ureteric bud (UB). A number of transcription and growth factors regulate UB branching morphogenesis to ultimately form the ureter, pelvis, calyces, medullary, and cortical collecting ducts. Importantly, UB morphogenesis is a key developmental process that controls organogenesis of the entire metanephros. This review emphasizes emerging insights into the role for the RAS in UB morphogenesis and explores the mechanisms whereby RAS regulates this important process. A conceptual framework derived from recent work indicates that cooperation between the angiotensin II AT(1) receptor and receptor tyrosine kinase signaling performs essential functions during renal collecting system development via control of UB branching morphogenesis.

A new role for the renin-angiotensin system in the development of the ureteric bud and renal collecting system

The renin-angiotensin system (RAS) plays a critical role in kidney development. Mutations in the genes encoding components of the RAS or pharmacological inhibition of RAS in mice or humans cause a spectrum of congenital abnormalities of the kidney and urinary tract (CAKUT). The observed defects include renal vascular abnormalities, abnormal glomerulogenesis, renal papillary hypoplasia, hydronephrosis, aberrant ureteric bud (UB) budding, duplicated collecting system and renal tubular dysgenesis. Little is known about the potential role of Ang II and its receptors in the morphogenesis of the UB and renal collecting system. This review emphasizes a novel role for the RAS in the development of the UB, collecting ducts and renal medulla. We observe that UB and surrounding stroma express angiotensinogen and Ang II AT1 receptors (AT1R) in vivo. Ang II stimulates UB cell branching in collagen gel cultures in vitro and induces UB morphogenesis in intact whole embryonic metanephroi grown ex vivo. In contrast, treatment of metanephroi with the AT1R antagonist candesartan inhibits UB branching. In addition, Ang II induces tyrosine phosphorylation of the epidermal growth factor receptor (EGFR) in UB cells. Furthermore, Ang II-stimulated UB morphogenesis is abrogated by inhibition of EGFR tyrosine kinase activity. In summary: 1) Ang II, acting via the AT1R, stimulates UB branching; 2) This process depends on tyrosine phosphorylation of the EGFR. Together, these data indicate that cooperation of AT1R and EGFR signaling performs essential functions during renal collecting system development via control of UB branching morphogenesis.

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.

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.

Role of the renin-angiotensin system in the development of the ureteric bud and renal collecting system

Genetic, biochemical and physiological studies have demonstrated that the renin-angiotensin system (RAS) plays a fundamental role in kidney development. All of the components of the RAS are expressed in the metanephros. Mutations in the genes encoding components of the RAS in mice or pharmacological inhibition of RAS in animals or humans cause diverse congenital abnormalities of the kidney and lower urinary tract. The latter include renal vascular abnormalities, abnormal glomerulogenesis, renal papillary hypoplasia, hydronephrosis, aberrant UB budding, duplicated collecting system, and urinary concentrating defect. Thus, the actions of angiotensin (ANG) II during kidney development are pleiotropic both spatially and temporally. Whereas the role of ANG II in renovascular and glomerular development has received much attention, little is known about the potential role of ANG II and its receptors in the morphogenesis of the collecting system. In this review, we discuss recent genetic and functional evidence gathered from transgenic knockout mice and in vitro organ and cell culture implicating the RAS in the development of the ureteric bud and collecting ducts. A novel conceptual framework has emerged from this body of work which states that stroma-derived ANG II elicits activation of AT(1)/AT(2) receptors expressed on the ureteric bud to stimulate branching morphogenesis as well as collecting duct elongation and papillogenesis.

Angiotensin II regulation of ovine fetoplacental artery endothelial functions: interactions with nitric oxide

During normal pregnancy, elevated angiotensin II (Ang II) concentrations in the maternal and fetal circulations are associated with dramatic increases in placental angiogenesis and blood flow. Much is known about a local renin-angiotensin system within the uteroplacental vasculature. However, the roles of Ang II in regulating fetoplacental vascular functions are less well defined. In the fetal placenta, the overall in vivo vasoconstrictor responses of the blood vessels to Ang II infusion is thought to be less than that in its maternal counterpart, even though infused Ang II induces vasoconstriction. Recent data from our laboratories suggest that Ang II stimulates cell proliferation and increases endothelial nitric oxide synthase (eNOS) and production of nitric oxide (NO) in ovine fetoplacental artery endothelial cells. These data imply that elevations of the known vasoconstrictor Ang II in the fetal circulation may indeed play a role in the marked increases in fetoplacental angiogenesis and that Ang II-elevated endothelial NO production may partly attenuate Ang II-induced vasoconstriction on vascular smooth muscle. Together with both of these processes, the high levels of Ang II in the fetal circulation may serve to modulate overall fetoplacental vascular resistance. In this article, we review currently available data on the expression of Ang II receptors in the ovine fetal placenta with particular emphasis on the effects of Ang II on ovine fetoplacental endothelium. The potential cellular mechanisms underlying the regulation of Ang II on endothelial growth and vasodilator production are discussed.

Vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF) expression during induced luteolysis in the bovine corpus luteum

Angiogenic factors, like vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF), and their receptors, are strongly regulated during the development of bovine corpus luteum (CL). The aim of this study was to investigate real-time changes of these factors in luteal tissue of cows (n = 4-5 per group) in the mid-luteal phase (day 8-12) after intramuscular injection of the PGF2alpha-analog Cloprostenol. Before (control) and 2, 4, 12, 48, and 64 hr after prostaglandin (PG) injection, CL were collected by transvaginal ovariectomy. RT-PCR for VEGF, VEGF-receptor type 1 (VEGF-R1), VEGF-R2, acidic FGF (FGF-1), basic FGF (FGF-2), and FGF-receptor (FGF-R) was performed. Additionally, the protein concentration for VEGF was determined. The mRNA expression of VEGF and its two receptors (VEGF-R1 and -R2) was significantly downregulated during structural luteolysis (after 12 hr). VEGF protein concentration already significantly declined 2 hr after PGF2alpha. Surprisingly FGF-1 and FGF-2 were significantly and maximally upregulated during functional luteolysis (until 12 hr). Furthermore, FGF-R mRNA was significantly upregulated at 2 hr after PGF2alpha, when compared with the control group. During structural luteolysis, the expression of FGFs and their receptors was not significantly different from control, except FGF-2 mRNA, which was downregulated at 64 hr. We conclude that the cessation of VEGF-support for the CL plays a role during structural luteolysis, whereas FGFs seem to have a major impact on functional luteolysis. The possible role of these growth factors could be a transient counter-regulation of luteolysis, but also an involvement in preventing inflammatory reactions during luteal regression.

Vascular control of ovarian function: ovulation, corpus luteum formation and regression

Hemodynamic changes are involved in the cyclic remodeling of ovarian structures. A transrectal color Doppler ultrasonography was used to assess the blood flow and changes in the vasculature that take place in the follicle wall and within the corpus luteum (CL) during specific physiological events such as ovulation, CL development, and CL regression in cows. To investigate the local release of vasoactive peptides, steroid hormones, and prostaglandins (PGs) in the ovarian microenvironment, the capillary membranes (0.2mm diameter and 5-10mm length) of a microdialysis system (MDS) were implanted into the follicle wall and the CL in vitro. Furthermore, in vivo experiments were conducted with the same MDS membranes surgically implanted in follicle wall or on CL along with ovarian venous and jugular catheters to collect simultaneous, real-time information on the ovarian and systemic changes in the secretion of factors regulating vascular function. Based on the results obtained from the series of in vitro and in vivo experiments, we propose that a functional "cross-talk" occurs between the vascular components (endothelial cells) and steroidogenic cells to control follicular and luteal functions in the bovine ovary.

Involvement of Pro-Inflammatory Cytokines, Mediators of Inflammation, and Basic Fibroblast Growth Factor in Prostaglandin F2α-Induced Luteolysis in Bovine Corpus Luteum1

The process of luteolysis requires very subtly modulated coordination of different factors and regulation systems. Immune cells and cytokines were shown to be relevant for bovine luteolysis. The aim of this study was to investigate the detailed pattern of mRNA expression of the pro-inflammatory cytokines tumor necrosis factor alpha (TNFalpha), TNF receptor type 1 (TNF-R1), interleukin 1beta (IL-1beta), and interferon gamma (IFNgamma), and of the inducible nitric oxide synthase (iNOS) and the basic fibroblast growth factor (FGF-2) during prostaglandin (PG) F(2alpha)-induced luteolysis in the bovine corpus luteum (CL). In addition, the mRNA expression for the LH-receptor (LH-R) and the steroidogenic enzyme p450scc was determined. Cows in the midluteal phase (Days 8-12) were injected with the PGF(2alpha) analogue cloprostenol, and CL were collected by transvaginal ovariectomy before and 2, 4, 12, 48, and 64 h after PGF(2alpha) injection. Conventional and real-time reverse transcription polymerase chain reaction RT-PCR (LightCycler) using SYBR Green I detection were employed to determine the mRNA expression for the investigated factors. All cytokines were significantly up-regulated during induced luteolysis. LH-R and p450scc mRNA were down-regulated (P < 0.05) during structural luteolysis (after 12 h), and p450scc in addition at 2 h after PGF(2alpha) (P < 0.05). FGF-2 expression increased (P < 0.001) during functional luteolysis (until 12 h after PGF(2alpha)) and diminished thereafter. The mRNA expression for iNOS decreased (P < 0.05) after induction of luteolysis. In conclusion, cytokines may be involved not only in structural but also in functional luteolysis and the deprivation of luteal survival factors, leading to a situation where apoptosis can occur. FGF-2 may participate in the suppression of cytokine-induced iNOS mRNA expression and in the prevention of an inflammatory reaction in the surrounding tissues.

The effect of acetylsalicylic acid and captopril on uterine and ovarian blood flow during the estrous cycle in mares

In previous studies, transrectal color Doppler sonography was used to demonstrate an increase in genital blood flow resistance in subfertile mares. The objectives of the present study were to determine the effects of an anticoagulant (acetylsalicylic acid) and a vasodilator (captopril) on uterine and ovarian perfusion and plasma progesterone concentrations in cycling mares. From Day 1 to 11 of an estrous cycle (Day 0=day of ovulation following prostaglandin-induced luteolysis), five Trotter mares were given 2500 mg lactose, 2500 mg ASA, or 50 mg captopril twice daily in their feed (one compound per cycle, in random order). Transrectal color Doppler sonography was used to examine both uterine arteries and the ovarian artery ipsilateral to the corpus luteum once daily, immediately prior to administration of the drug. Blood flow resistance was determined semiquantitatively using the pulsatility index (PI) and plasma progesterone concentrations were determined with an enzyme immunoassay. Compared to the placebo, both ASA and captopril decreased mean PI values of both uterine arteries of all mares. On average, ASA decreased the PI of the uterine arteries by 25%; this was more (P<0.05) than the average decrease (13%) caused by captopril. Both drugs decreased (P<0.05) blood flow resistance in the ovarian arteries, although there was no difference (P<0.05) in their efficacy. In addition, both ASA and captopril increased (P<0.0001) plasma progesterone concentrations (18 and 17%, respectively). In conclusion, either ASA or captopril improved uterine and ovarian perfusion; however the effects on fertility were not determined.

A role for angiotensin II AT1 receptors in ureteric bud cell branching

Gene-targeting studies in mice demonstrate that the renin-angiotensin system is required for the proper development of the renal medulla. In the absence of angiotensin II (ANG II) or the ANG II type 1 (AT1) receptor, mice exhibit poor papillary development and a severe urinary-concentrating defect. These findings imply that the ureteric bud (UB) and its branches are targets for ANG II actions during renal development. However, direct evidence linking ANG II with UB-branching morphogenesis does not exist. Using immunohistochemistry, we demonstrated that UB-derived epithelia express angiotensinogen (Ao) and the AT1 receptor during murine metanephrogenesis. Ao and AT1 receptors are expressed in the UB branches and to a lesser extent in the stromal mesenchyme. AT1 receptor expression in UB-derived epithelia increased from embryo day 12 to day 16 and was observed on both luminal and basolateral membranes. In accord with these findings, cultured murine UB cells express AT1 receptor protein and mRNA. Treatment of UB cells cultured in three-dimensional type I collagen gels with ANG II (10-7 to 10-5 M) elicits a dose-related increase in the number of cells that have primary and secondary branches. These effects of ANG II on UB branching are abrogated by pretreatment with the AT1 receptor antagonist candesartan. These data demonstrate a direct and independent role for ANG II acting via AT1 receptors on UB cell branching in vitro. The presence of Ao in the stroma and AT1 on UB cells supports the notion that cross talk between stroma and epithelial cells is crucial to epithelial branching morphogenesis in the developing kidney.

Real-time changes of the local vasoactive peptide systems (angiotensin, endothelin) in the bovine corpus luteum after induced luteal regression

There is evidence that angiotensin II (Ang II) and endothelin-1 (ET-1) may interact in an additive or synergistic way during luteal regression. The aim of the study was to investigate real time changes in luteal tissue of angiotensin and endothelin system members in mRNA expression, tissue concentrations, tissue localization, and ACE (angiotensin converting enzyme) antagonist application after prostaglandin F(2alpha) (PG) induced (days 8-12) luteal regression in cow. Corpora lutea (CL) were collected by transvaginal ovaryectomy before and 2, 4, 12, 24, 48, and 64 hr (n = 5/time point) after PG injection. ACE mRNA expression (RT-PCR) increased continuously and peaked at 12, 24 hr; ECE-1 (endothelin converting enzyme) peaked at 12 hr, and both peptides in tissue (Ang II and ET-1) increased significantly and peaked at 24 hr. The expression of receptors for Ang II (AT1R and AT2R) did not change in contrast to ET receptors (ETR-A and ETR-B), which were up-regulated. Localization in tissue revealed very weak staining for Ang II and ET-1 before PG application followed by a clear increase of staining predominantly in large luteal cells, but also in endothelial cells. In two experiments, the attempt was made to block ACE by the antagonist captopril with two different doses. In both experiments with captopril, progesterone levels were not significantly different from controls. Ang II alone seems to be not essential for functional luteolysis in bovine system. In conclusion, the results suggest that both Ang II and ET-1 are in parallel up-regulated during luteal regression and may act as vasoconstrictors during functional luteolysis, but also as apoptosis inducer during functional/structural luteolysis.

[Revisiting the role of LH in follicular development]

During the last decade, two pivotal events widened the gap between the hormonal dynamics of ovarian stimulation and that of the menstrual cycle. First, the profound and routine suppression of endogenous gonadotropins by GnRH analogues used in ovarian stimulation pressed us to recreate the hormonal environment necessary for adequate follicular maturation and steroidogenesis. Second, drugs with reduced or null LH activity became available, based on the hypothesis that FSH action was sufficient to follicular development and maturation irrespective of residual endogenous gonadotropin levels. Today, there is a renewed interest in the possible role of LH on follicular development, in an effort to mimic the hormonal events of the menstrual cycle to optimize ovarian stimulation outcome.

Intraluteal release of angiotensin II and progesterone in vivo during corpora lutea development in the cow: effect of vasoactive peptides

The newly formed corpus luteum (CL) develops rapidly and has the features of active vascularization and mitosis of steroidogenic cells. Such local mechanisms must be strictly regulated by the complex relationship between angiogenic growth factors and vasoactive peptides such as angiotensin (Ang) II, atrial natriuretic peptide (ANP), and endothelin (ET)-1. Thus, the objective of the present study was to determine 1) the changes in vasoactive peptides and progesterone (P) concentrations within the developing CL, along with the changes in concentration in ovarian venous plasma (OVP) and jugular venous plasma (JVP) in the cow, 2) the effects of CL exposure to vasoactive peptides on Ang II and P secretion, and 3) the expression of mRNA for ANP type C receptor in the bovine CL and endothelial cells (ETC) from bovine developing CL. A microdialysis system (MDS) was surgically implanted into multiple CL of six cows on Day 3 after a GnRH injection that induced superovulation, and a catheter was simultaneously inserted into the ovarian vein. The Ang II concentration in OVP was higher than that in JVP throughout the experiment, while the intraluteal release of Ang II was stable. During the experimental period, the concentrations of other vasoactive peptides (ANP and ET-1) showed no clear changes in plasma and were below detectable levels in the MDS perfusate. Exposure of CL to Ang II using the MDS stimulated P release, while exposure to ANP enhanced Ang II release within the developing CL. However, ET-1 had no effect on either P or Ang II release. The expression of mRNA for ANP type C receptor was mainly observed in early CL and ETC. The results suggest that the ET-Ang-ANP system in the preovulatory follicle switches to an Ang-ANP system to enhance both the angiogenesis and steroidogenesis that are actively occurring in developing CL.

Localization of the renin-angiotensin system in the bovine ovary: cyclic variation of the angiotensin II receptor expression

Angiotensin (Ang) II may modulate reproductive function in the bovine ovary. Therefore, expression and localization of a local ovarian renin-angiotensin system (RAS) were investigated by elucidating the influence of the estrus cycle, pregnancy, and the presence of follicular cysts. Receptor analysis and autoradiography were used to characterize and localize Ang II receptors. Cyclic variations in the density of ovarian Ang II receptors were found with a higher value in estrus than in diestrus. The density in ovaries with follicular cysts was in the same order of magnitude as in estrus. The Ang II receptor type 2 (AT(2)) dominated in all three groups. Autoradiography showed that the majority of antral follicles and follicular cysts had intense AT(2) receptor binding in the theca externa. Binding was less intense in the theca interna, whereas there was no binding in the granulosa layer. In the corpora lutea, the AT(2) receptor was dominant in the capsule and in connective tissue infoldings, whereas no binding was observed in the luteal tissue. The type 1 Ang II receptor (AT(1)) was dominant in the stroma and showed no cyclic changes. Angiotensin-converting enzyme (ACE) activity was detected in all aspirated follicular fluids and homogenates of ovarian tissue. Autoradiography showed that most of the ACE was localized on endothelial cells. Renin immunoreactivity was found in granulosa and thecal cells of antral follicles and in luteal cells. Furthermore, solitary cells in the stroma, presumably macrophages, displayed intense staining. Our finding of cyclic changes support the concept of an active and regulated RAS in the bovine ovary.

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.

A short total synthesis of (+)-furanomycin

[reaction: see text] Furanomycin is a Streptomyces metabolite that substitutes for isoleucine in protein translation. We report a concise and modular synthesis starting from the Garner aldehyde and proceeding in seven steps to furanomycin. The key steps include a stereoselective acetylide addition and the Ag+-mediated cyclization of an alpha-allenic alcohol to construct the trans-2,5-dihydrofuran. The efficiency (12% overall yield) and flexibility of the route will provide ample quantities of furanomycin and analogues for protein engineering.

Regulation of angiotensin II production and angiotensin receptors in microvascular endothelial cells from bovine corpus luteum

Recent findings suggest that the ovarian renin-angiotensin system regulates ovarian function through the paracrine/autocrine actions of angiotensin (Ang) II. The aims of this study were to investigate 1) the endothelial cell capacity to convert Ang I to Ang II, 2) the effects of endocrine and paracrine/autocrine factors on Ang II production in microvascular endothelial cells (MVE) derived from the developing corpora lutea (CL), and 3) the relationship between Ang II peptide concentration and expression of mRNA for angiotensin type 1 and 2 receptors (ATR1 and AT2R) in the bovine CL at different stages of the estrous cycle. When Ang I was added to the MVE at a concentration of 10(-9) M, it was converted to Ang II (21%). The production of Ang II from Ang I time-dependently rose for 24 h. Addition of captopril (an inhibitor of Ang-converting enzyme [ACE]) to the MVE cultures significantly inhibited Ang II production from 6 h to 24 h (P < 0.05). Addition of estradiol-17beta (E(2)) + vascular endothelial growth factor and E(2) + basic fibroblast growth factor to MVE cultures increased Ang II production, whereas E(2) or growth factors alone had no effect. Specific transcription for AT1R and AT2R was detected in bovine CL and MVE. There were no significant changes in Ang II tissue concentration or AT1R mRNA expression using reverse transcription-polymerase chain reaction during the estrous cycle. In contrast, AT2R mRNA expression decreased during the midluteal phase (P < 0.05) and increased to the highest level during the late luteal phase (P < 0.05). Results demonstrated that Ang II is generated from Ang I in MVE isolated from the developing bovine CL, indicating that MVE have ACE activity. In addition, mRNA expression for Ang II receptors was detected in the bovine CL and the luteal MVE. These results suggest that Ang II is produced by actions of the local renin-angiotensin system, at least in part, on MVE in the bovine CL, and that this peptide may be involved in the regulation of luteal function during early development and luteolysis.

Angiotensin II interacts with prostaglandin F2alpha and endothelin-1 as a local luteolytic factor in the bovine corpus luteum in vitro

Recent findings suggest that the ovarian renin-angiotensin system may regulate ovarian function through the paracrine/autocrine actions of angiotensin II (Ang II). In this study, we have examined and characterized the local effects of Ang II as a luteolytic factor and its interaction with prostaglandin F2alpha (PGF2alpha) and endothelin-1 (ET-1) in the bovine corpus luteum (CL) of the mid-luteal phase, by using an in vitro microdialysis system (MDS). Ang II was detected in the MDS perfusate (4 pg/ml), and infusion of PGF2alpha (10(-6) M) for 2 h increased the Ang II release by 50-100% during the following experimental period, in addition to its stimulation of ET-1 release. Two 2-h infusions of Ang II (10(-7)-10(-5) M) separated by a 2-h interval induced a dose- and time-dependent decrease of progesterone (P4) release by 41-66%. When the luteal explants were pre-perfused with PGF2alpha (10(-6) M) for 2 h, two consecutive perfusions of Ang II (10(-6) M) at a 2-h interval rapidly reduced the P4 release (by 50%). This reduction occurred 6 h earlier than those of infusions of PGF2alpha or Ang II alone. The simultaneous infusion of either 1) Ang II (10(-6) M) with PGF2alpha (10(-6) M), 2) ET-1 (10(-7) M) with PGF2alpha, or 3) Ang II + ET-1 with PGF2alpha (10(-6) M) for 2 h also induced a rapid and pronounced (60%) decrease in P4 release. Perfusion with the Ang II antagonist blocked the P4-suppressing activity of Ang II alone or PGF2alpha + Ang II infusion. Ang II stimulated the release of ET-1 and oxytocin during infusion but inhibited them after infusion. These results show that Ang II is released in the bovine midcycle CL in vitro, and this peptide, either alone or together with PGF2alpha, can suppress the release of P4. As PGF2alpha directly stimulated Ang II release, Ang II may influence the critical period for starting the cascade of functional luteolysis in vivo and might lead to structural luteolysis with ET-1 as a major vasoconstrictor. The overall results suggest that Ang II may have an important role at luteolysis in the bovine CL.

Different modulation of steroidogenesis and prostaglandin production in frog ovary in vitro by ACE and ANG II

Our aim was to study the role of angiotensin-converting enzyme (ACE) and angiotensin II (ANG II) on ovarian steroidogenesis and prostaglandin production of amphibian. Hormonal effects of ACE, ACE inhibitors, synthetic bullfrog angiotensin I (ANG I), and [Val5]ANG II were compared on frog ovaries of postreproductive and prereproductive periods. Very high ACE activity was found in ovary of water frog (Rana esculenta) compared with other frog tissues, and this activity was inhibited by the typical ACE inhibitors, captopril and lisinopril. Frog ovary tissue in postreproductive and prereproductive periods was incubated in vitro in the presence of ACE (2.5 mU/ml), captopril (0.1 mM), lisinopril (0.1 mM), [Val5]ANG II (1 microM), and synthetic bullfrog ANG I (1 microM). Production of 17 beta-estradiol, progesterone, androgens, and prostaglandins E2 and F2 alpha was determined. The data showed a modulation of 17 beta-estradiol, progesterone, and prostaglandin E2 production by ovary ACE; on the other hand, [Val5]ANG II modulated the production of progesterone and prostaglandin F2 alpha, whereas androgen production was not influenced. The present in vitro studies suggest the existence of two pathways independently regulated by ACE and ANG II modulating ovarian steroidogenesis and prostaglandin production.

A CRE-like sequence that binds CREB and contributes to cAMP-dependent regulation of the proximal promoter of the human aromatase P450 (CYP19) gene

The major physiological regulator of human aromatase P450 gene expression in the ovary is follicle stimulating hormone (FSH), which acts by increasing intracellular cAMP levels. This study describes the identification of an element in the aromatase proximal promoter that is critical for the full transcriptional response of this promoter to cAMP. The cAMP-responsive element (CRE)-like sequence (CLS) was originally identified by its sequence similarity to a palindromic CRE, from which it differs by the insertion of a single cytosine. Mutation of the CLS in the context of 278 bp of 5'-flanking DNA resulted in the loss of cAMP-induced reporter gene expression in transfected ovarian luteal cells. A cell line survey EMSA revealed that CLS binding factors are ubiquitously distributed, although the migration pattern of CLS-nuclear protein complexes varied among different nuclear extracts. An extended half-site for binding members of the basic-leucine zipper class of transcription factors was found to be responsible for ovarian luteal cell nuclear protein binding and cAMP-dependent transcriptional transactivation. Competition and supershift EMSAs revealed that the CLS-nuclear protein complexes that regulate cAMP-induced transcription were indistinguishable from homodimeric CREB bound to the CRE oligonucleotide, yet the interaction with the CLS was of lower affinity.

The 5'-flanking region of the ovarian promoter of the bovine CYP19 gene contains a deletion in a cyclic adenosine 3',5'-monophosphate-like responsive sequence

Conversion of C19 steroids to estrogens is catalyzed by aromatase P450 (P450arom; the product of the CYP19 gene). In the ovary, P450arom is expressed in granulosa cells of both human (h) and bovine (b) follicles. After the ovulatory surge of gonadotropins, however, P450arom expression is maintained only in the luteinized granulosa cells of the human ovary and is absent from the bovine corpus luteum. We compared the regulation of expression of the ovary-specific human CYP19 (hCYP19ov) and the bovine CYP19 (bCYP19ov) gene by cAMP (forskolin) and sought to determine whether the divergence in the expression of P450arom with the onset of luteinization could be explained by specific cis-acting elements present uniquely in the 5'-flanking DNA of the hCYP19ov or bCYP19ov gene. We, therefore, subcloned DNA encompassing the promoters and 5'-flanking regions of the hCYP19ov or bCYP19ov gene into a promoterless luciferase vector. These constructs were transfected into luteinized bovine granulosa cells or bovine luteal cells in primary culture. Neither cell type exhibits endogenous expression of bovine P450arom. After transfection, cells were treated with either vehicle or 25 microM forskolin. There was little or no increase in luciferase activity after forskolin treatment in cells transfected with any of the bCYP19ov constructs, whereas all of the corresponding hCYP19ov constructs (-693/-16 to -214/-16 bp) expressed reporter activity in the presence of forskolin. This dramatic difference between the activities of the constructs of the two species occurred despite the fact that there is an 88% sequence identity between the bovine and human promoters in the region between -214 to -16 bp. One possible explanation for this variability may be that the bCYP19ov gene has a 1-bp deletion in a cAMP-response element-like sequence (CLS) present at -208 to -201 bp in the hCYP19ov gene that we have shown to be critical for cAMP-stimulated transcription of hCYP19ov in the ovary. When this region of the bCYP19ov promoter was mutated to the hCLS, a partial restoration in luciferase activity was observed after forskolin treatment. Therefore, these results suggest that another sequence in this -214 bp region of the bCYP19ov gene is also contributing to the lack of expression of P450arom after luteinization in the bovine ovary. This lack of expression of the bCYP19ov gene may be due to the presence of a repressive trans-acting factor expressed with the onset of luteinization of the bovine granulosa cell. These results further suggest that in the cow, elements upstream of those employed by the hCYP19ov gene may have been recruited to facilitate regulated expression of the bCYP19ov gene in the absence of a functional CLS.

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.

A putative binding site for Sp1 is involved in transcriptional regulation of CYP17 gene expression in bovine ovary

In the bovine ovary, thecal cells are the only cell type capable of expressing the CYP17 gene in response to LH. With the onset of ovulation and luteinization in the cow, there is complete loss of P450c17alpha expression. To characterize the molecular mechanisms involved in tissue-specific regulation of the CYP17 gene in the bovine ovary, deletion mutations of the bovine CYP17 promoter were ligated into a promoterless luciferase expression vector, and reporter constructs were transiently transfected into primary cultures of bovine thecal and luteal cells. Deletion of the promoter sequences between -191 and 101 bp dramatically decreased the levels of reporter gene activity in both thecal and luteal cells. Computer-assisted analysis revealed the presence of a putative inverted Sp1-like binding site at -188/-180 bp. Deletion or mutation of this sequence caused a decrease in both basal and forskolin-stimulated reporter gene activity. In addition, mutation or deletion of this sequence also decreased reporter gene expression induced by overexpression of the protein kinase A catalytic subunit. Electrophoretic mobility shift assays showed that this sequence binds to a nuclear protein(s) from both thecal and luteal cells that is related to Sp1, as suggested by the results of gel mobility supershift assay employing an antibody raised against Sp1. DNA-binding activity was not increased by the addition of forskolin to thecal or luteal cells. We conclude that this inverted Sp1-like binding sequence is involved in constitutive as well as cAMP-dependent expression of the CYP17 gene in the bovine ovary.

Modulation of cerebral calcium homeostasis in rats by angiotensin II in vivo

The uptake of 45Ca2+ by different regions of the brain was determined in anaesthetised rat after infusing angiotensin II (AII; 14 micrograms in 1 ml) through the carotid artery. The control animals (C) were infused with physiological saline. 45Ca2+ was injected in the tail vein 2 min after the infusion of AII or saline. Plasma radioactivity was monitored until euthanasia at different times post injection when the cerebral uptake of 45Ca2+ was determined. While the plasma turnover of 45Ca2+ was similar in AII and C animals, the uptake was markedly higher in AII vs. C at the different brain sites at all times. Kinetic analysis suggested that AII induced a short term increase in Ca2+ transport across the blood-brain barrier and also in the cellular uptake. The effect of AII was receptor mediated being abolished by saralasin, an AII antagonist, and appeared to be at least in part independent of its pressor effect.

Bioactive angiotensin (1-8) is the main component of angiotensin II immunoreactivity in human follicular fluid

The ovarian renin-angiotensin system is involved in various aspects of human reproduction. As immunoreactive measurement of angiotensin II (ANG II) in follicular fluid (FF) relates to several angiotensin peptides with different biological activities, HPLC was used to characterize the molecular forms of the ANG II immunoreactivity in human FF. Samples of FF, obtained from gonadotropin-stimulated patients for in vitro fertilization, were collected at the time of oocyte retrieval. The C-terminal 2-8 heptapeptide was never detected. HPLC analysis revealed for the first time that the major component of the ANG II-IR in human FF was the biologically active octapeptide ANG II.

Regulation of cholesterol side-chain cleavage cytochrome P450 in mouse testis Leydig cell line I-10

We have characterized regulation of steroidogenesis in a mouse testis Leydig cell line, I-10. Progesterone secretion was increased in a time- and dose-dependent fashion by 8-Br-cAMP treatment. The amount of cholesterol side-chain cleavage enzyme (P450scc), the first and rate-limiting enzyme for the synthesis of steroids, as detected by immunoblotting, was also increased. The calcium ionophore A23187 decreased the amount of P450scc, but it did not interfere with cAMP stimulation of the accumulation of P450scc. This regulation of P450scc expression by cAMP and A23187 is at the post-transcriptional level because the amount of P450scc mRNA was not affected by either treatment. This result was further confirmed by direct measurement of transcription in the presence or absence of forskolin treatment. I-10, however, supported cAMP-dependent transcriptional activation of the exogenous gene, as shown by the increased expression of a reporter gene under the control of the -600 to -2,500 fragment of the P450scc gene. The ability for transcriptional activation of the exogenous but not endogenous P450scc gene makes I-10 a unique steroidogenic cell line.

Ad4BP/SF-1 regulates cyclic AMP-induced transcription from the proximal promoter (PII) of the human aromatase P450 (CYP19) gene in the ovary

Aromatase P450, which is responsible for the metabolism of C19 steroids to estrogens, is expressed in the pre-ovulatory follicles and corpora lutea of ovulatory women by means of a promoter proximal to the start of translation (PII). To understand how this transcription is controlled by cAMP, we constructed chimeric constructs containing deletion mutations of the proximal promoter 5'-flanking DNA fused to the rabbit beta-globin reporter gene. Assay of reporter gene transcription in transfected bovine granulosa and luteal cells revealed that cAMP-stimulated transcription was lost upon deletion from -278 to -100 base pairs, indicating the presence of a functional cAMP-responsive element in this region; however, no classical cAMP-responsive element was found. Mutation of an AGGTCA motif located at -130 base pairs revealed that this element is crucial for cAMP-stimulated reporter gene transcription. When a single copy of this element was placed upstream of a heterologous promoter, it could act as a weak cAMP-response element. Supershift electrophoretic mobility shift assay and UV cross-linking established that Ad4BP/SF-1 binds to this hexameric element. Ad4BP/SF-1 mRNA and protein levels and DNA binding activity are increased in forskolin-treated luteal cells. We conclude that cAMP-stimulated transcription of human aromatase P450 in the ovary is due, at least in part, to increased levels and DNA binding activity of Ad4BP/SF-1.

Reproduction and the renin-angiotensin system

A unique aspect of the circulating renin-angiotensin system and the many independent tissue renin-angiotensin systems is their interactions at multiple levels with reproduction. These interactions, which have received relatively little attention, include effects of estrogens and possibly androgens on hepatic and renal angiotensinogen mRNA; effects of androgens on the Ren-2 gene and salivary renin in mice; the prorenin surge that occurs with but outlasts the LH surge during the menstrual cycle; the inhibitory effects of estrogens on thirst and water intake; the tissue renin-angiotensin systems in the brain, the anterior pituitary, and the ovaries and testes, that is, in all the components of the hypothalamo-pituitary-gonadal axis; the presence of some components of the renin-angiotensin system in the uterus and the fetoplacental unit; and the possible relation of renin and angiotensin to ovulation and fetal well-being. These interactions are described and their significance considered in this short review.

Angiotensin converting enzyme inhibition of the gonadotropin-stimulated rabbit: effect on estradiol production

PURPOSE

Our purpose was to determine whether angiotensin converting enzyme (ACE) inhibitors affect gonadotropin-stimulated estradiol (E2) production.

DESIGN

This was a prospective, masked, randomized, placebo-controlled animal trial. Twenty female New Zealand White rabbits were hyperstimulated with gonadotropins. One-half of the rabbits received concomitant treatment with the ACE inhibitor, enalapril; one-half received concomitant treatment with a placebo.

RESULTS

Baseline peripheral E2 (13 +/- 4 vs 11 +/- 2 pg/ml) and angiotensin II (Ang II) (22 +/- 5 vs 27 +/- 7 pg/ml) levels were similar in both groups. Significant inhibition of peripheral Ang II levels was achieved in the enalapril group (32 +/- 6 vs 93 +/- 15 pg/ml; P = 0.005). E2 was significantly higher in the rabbits receiving enalapril versus placebo (369 +/- 58 vs 183 +/- 35 pg/ml, P < 0.03), respectively. By day 10, peripheral E2 had returned to normal levels in both groups (13 +/- 1 vs 13 +/- 1 pg/ml). However, E2 levels in the ovarian effluent were 2.8 times higher in the enalapril rabbits.

CONCLUSION

Peripheral Ang II levels increase after gonadotropin stimulation and ACE inhibitors are able to blunt this increase significantly. ACE inhibition has a significant stimulatory effect on ovarian E2 production. This implies that Ang II may normally inhibit ovarian E2 production in stimulated cycles.

Inhibition of hydroxymethylglutaryl coenzyme A reductase activity does not affect the secretion rate of apolipoproteins B and AI by CaCo-2 cells

It is believed that the major mechanisms by which hydroxymethylglutaryl coenzyme A reductase inhibitors lower plasma cholesterol levels are by inducing hepatic low-density lipoprotein (LDL) receptor activity and by decreasing apolipoprotein B (apoB) secretion by the liver. However, the intestine is also an important cholesterogenic organ and the possibility that this class of drugs may alter lipoprotein secretion by the intestine has not been fully studied. The purpose of the present study was to examine the possible role of cholesterol in regulating apoB secretion by the intestine by testing if the suppression of cholesterol synthesis by the reductase inhibitor lovastatin affected the secretion of apoB by CaCo-2 human intestinal cells. Differentiated post-confluent CaCo-2 cells were incubated for 24-72 h in serum-free medium in the presence or absence of 5 microM lovastatin, and the secretion rate of lipids, as well as apoB and apolipoprotein AI (apoAI) into the medium, was measured. Lovastatin markedly inhibited the incorporation of [1-14C]acetate into cholesterol for at least 48 h, lowered the content of esterified cholesterol in cells, and reduced their rate of cholesterol secretion. However, under basal conditions lovastatin had no effect on the secretion rate of apoB. After stimulation of apoB secretion by addition of 0.8 mM oleic acid to the medium, lovastatin did not alter apoB secretion in the first 2 days of incubation, but reduced the content of apoB in media from the 3rd day by 30%. This could not be explained by an increase in the rate of LDL degradation. Furthermore, supplementation with mevalonic acid only reversed about one-half of the effect of lovastatin, suggesting that this effect was at least parly nonspecific or unrelated to inhibition of cholesterol biosynthesis. There was also no specific effect of lovastatin on apoAI secretion. When cells were cultured with [1-14C]acetate for 24 or 72 h, the specific activity of cholesterol in medium at the end of the incubation was the same as in cells, suggesting that cholesterol used for lipoprotein secretion was in equilibrium with bulk cellular cholesterol and was not from a segregated compartment derived from newly synthesized cholesterol. This may explain why apoB secretion by CaCo-2 cells was unaffected by inhibition of cholesterol synthesis with lovastatin.