Perinatal ANG II programs adult blood pressure, glomerular number, and renal function in rats

Effects of Voluntary Sodium Consumption during the Perinatal Period on Renal Mechanisms, Blood Pressure, and Vasopressin Responses after an Osmotic Challenge in Rats

Cardiovascular control is vulnerable to forced high sodium consumption during the per-inatal period, inducing programming effects, with anatomical and molecular changes at the kidney, brain, and vascular levels that increase basal and induce blood pressure. However, the program- ming effects of the natriophilia proper of the perinatal period on blood pressure control have not yet been elucidated. In order to evaluate this, we studied the effect of a sodium overload challenge (SO) on blood pressure response and kidney and brain gene expression in adult offspring exposed to voluntary hypertonic sodium consumption during the perinatal period (PM-NaCl group). Male PM-NaCl rats showed a more sustained increase in blood pressure after SO than controls (PM-Ctrol). They also presented a reduced number of glomeruli, decreased expression of TRPV1, and increased expression of At1a in the kidney cortex. The relative expression of heteronuclear vaso- pressin (AVP hnRNA) and AVP in the supraoptic nucleus was unchanged after SO in PM-NaCl in contrast to the increase observed in PM-Ctrol. The data indicate that the availability of a rich source of sodium during the perinatal period induces a long-term effect modifying renal, cardiovascular, and neuroendocrine responses implicated in the control of hydroelectrolyte homeostasis.

Inhibition of the AT1R agonistic autoantibody in a rat model of preeclampsia improves fetal growth in late gestation

Placenta ischemia, the initiating event in preeclampsia (PE), is associated with fetal growth restriction. Inhibition of the agonistic autoantibody against the angiotensin type 1 receptor AT1-AA, using an epitope-binding inhibitory peptide ('n7AAc') attenuates increased blood pressure at gestational day (G)19 in the clinically relevant reduced uterine perfusion pressure (RUPP) model of PE. Thus we tested the hypothesis that maternal administration of 'n7AAc' does not transfer to the fetus, improves uterine blood flow and fetal growth, and attenuates elevated placental expression of miRNAs implicated in PE and FGR. Sham or RUPP surgery was performed at G14 with vehicle or 'n7AAc' (144 µg/day) administered via an osmotic pump from G14 to G20. Maternal plasma levels of the peptide on G20 were 16.28 ± 4.4 nM, and fetal plasma levels were significantly lower at 1.15 ± 1.7 nM (P = 0.0007). The uterine artery resistance index was significantly elevated in RUPP (P < 0.0001) but was not increased in 'n7AAc'-RUPP or 'n7AAc'-Sham versus Sham. A significant reduction in fetal weight at G20 in RUPP (P = 0.003) was not observed in 'n7AAc'-RUPP. Yet, percent survival was reduced in RUPP (P = 0.0007) and 'n7AAc'-RUPP (P < 0.0002). Correlation analysis indicated the reduction in percent survival during gestation was specific to the RUPP (r = 0.5342, P = 0.043) and independent of 'n7AAc'. Placental miR-155 (P = 0.0091) and miR-181a (P = 0.0384) expression was upregulated in RUPP at G20 but was not elevated in 'n7AAc'-RUPP. Collectively, our results suggest that maternal administration of 'n7AAc' does not alter fetal growth in the RUPP implicating its potential as a therapeutic for the treatment of PE.NEW & NOTEWORTHY The seven amino acid inhibitory peptide to the AT1-AA ('n7AAc') has limited transfer to the fetus at gestational day 20, improves uterine blood flow and fetal growth in the reduced uterine perfusion pressure model of preeclampsia (PE), and does not impair fetal survival during gestation in sham-operated or placental ischemic rats. Collectively, these findings suggest that maternal administration of 'n7AAc' as an effective strategy for the treatment of PE is associated with improved outcomes in the fetus.

The developmental origins of health and chronic kidney disease: Current status and practices in Japan

The concept of the developmental origins of health and disease (DOHaD) views unfavorable perinatal circumstances as contributing to the development of diseases in later life. It is well known that such unfavorable circumstances play an important role as a risk factor for chronic kidney disease (CKD) in infants born with prematurity. Low birthweight (LBW) is believed to be a potential contributor to CKD in adulthood. Preterm and/or LBW infants are born with incomplete nephrogenesis. As a result, the number of nephrons is low. The poor intrauterine environment also causes epigenetic changes that adversely affect postnatal renal function. After birth, hyperfiltration of individual nephrons due to low nephron numbers causes proteinuria and secondary glomerulosclerosis. Furthermore, the risk of CKD increases as renal damage takes a second hit from exposure to nephrotoxic substances and acquired insults such as acute kidney injury after birth among infants in neonatal intensive care. Meanwhile, unfortunately, recent studies have shown that the number of nephrons in healthy Japanese individuals is approximately two-thirds lower than that in previous reports. This means that Japanese premature infants are clearly at a high risk of developing CKD in later life. Recently, several DOHaD-related CKD studies from Japanese researchers have been reported. Here, we summarize the relevance of CKD in conjunction with DOHaD and review recent studies that have examined the impact of the upward LBW trend in Japan on renal health.

Animal Models for DOHaD Research: Focus on Hypertension of Developmental Origins

Increasing evidence suggests that fetal programming through environmental exposure during a critical window of early life leads to long-term detrimental outcomes, by so-called developmental origins of health and disease (DOHaD). Hypertension can originate in early life. Animal models are essential for providing convincing evidence of a causal relationship between diverse early-life insults and the developmental programming of hypertension in later life. These insults include nutritional imbalances, maternal illnesses, exposure to environmental chemicals, and medication use. In addition to reviewing the various insults that contribute to hypertension of developmental origins, this review focuses on the benefits of animal models in addressing the underlying mechanisms by which early-life interventions can reprogram disease processes and prevent the development of hypertension. Our understanding of hypertension of developmental origins has been enhanced by each of these animal models, narrowing the knowledge gap between animal models and future clinical translation.

Targeting the Renin-Angiotensin-Aldosterone System to Prevent Hypertension and Kidney Disease of Developmental Origins

The renin-angiotensin-aldosterone system (RAAS) is implicated in hypertension and kidney disease. The developing kidney can be programmed by various early-life insults by so-called renal programming, resulting in hypertension and kidney disease in adulthood. This theory is known as developmental origins of health and disease (DOHaD). Conversely, early RAAS-based interventions could reverse program processes to prevent a disease from occurring by so-called reprogramming. In the current review, we mainly summarize (1) the current knowledge on the RAAS implicated in renal programming; (2) current evidence supporting the connections between the aberrant RAAS and other mechanisms behind renal programming, such as oxidative stress, nitric oxide deficiency, epigenetic regulation, and gut microbiota dysbiosis; and (3) an overview of how RAAS-based reprogramming interventions may prevent hypertension and kidney disease of developmental origins. To accelerate the transition of RAAS-based interventions for prevention of hypertension and kidney disease, an extended comprehension of the RAAS implicated in renal programming is needed, as well as a greater focus on further clinical translation.

Calcitriol reduces kidney development disorders in rats provoked by losartan administration during lactation

Calcitriol has important effects on cellular differentiation and proliferation, as well as on the regulation of the renin gene. Disturbances in renal development can be observed in rats exposed to angiotensin II (AngII) antagonists during lactation period. The lack of tubular differentiation in losartan-treated rats can affect calcitriol uptake. This study evaluated the effect of calcitriol administration in renal development disturbances in rats provoked by losartan (AngII type 1 receptor antagonist) administration during lactation. Animals exposed to losartan presented higher albuminuria, systolic blood pressure, increased sodium and potassium fractional excretion, and decreased glomerular filtration rate compared to controls. These animals also showed a decreased glomerular area and a higher interstitial relative area from the renal cortex, with increased expression of fibronectin, alpha-SM-actin, vimentin, and p-JNK; and an increased number of macrophages, p-p38, PCNA and decreased cubilin expression. Increased urinary excretion of MCP-1 and TGF-β was also observed. All these alterations were less intense in the losartan + calcitriol group.The animals treated with calcitriol showed an improvement in cellular differentiation, and in renal function and structure. This effect was associated with reduction of cell proliferation and inflammation.

Antenatal corticosteroids and the renin-angiotensin-aldosterone system in adolescents born preterm

BACKGROUND

Antenatal corticosteroid (ANCS) treatment hastens fetal lung maturity and improves survival of premature infants, but the long-term effects of ANCS are not well-described. Animal models suggest that ANCS increases the risk of cardiovascular disease through programmed changes in the renin-angiotensin (Ang)-aldosterone system (RAAS). We hypothesized that ANCS exposure alters the RAAS in adolescents born prematurely.

METHODS

A cohort of 173 adolescents born prematurely was evaluated, of whom 92 were exposed to ANCS. We measured plasma and urine Ang II and Ang-(1-7) and calculated Ang II/Ang-(1-7) ratios. We used general linear regression models to estimate the difference in the RAAS between the ANCS-exposed and unexposed groups, adjusting for confounding variables.

RESULTS

In unadjusted analyses, and after adjustment for sex, race, and maternal hypertension, ANCS exposure was associated with increased urinary Ang II/Ang-(1-7) (estimate 0.27 (95% CI 0.03, 0.5), P = 0.03), increased plasma Ang-(1-7) (0.66 (0.26, 1.07), P = 0.002), and decreased plasma Ang II/Ang-(1-7) (-0.48 (-0.91, -0.06), P = 0.03).

CONCLUSION

These alterations indicate an imbalance in the urinary RAAS, promoting the actions of Ang II at the expense of Ang-(1-7), which over time may increase the risk of renal inflammation and fibrosis and ultimately hypertension and renal disease.

Increased renal apoptosis and reduced renin-angiotensin system in fetal growth restriction

OBJECTIVE

The purpose of the study was to characterize changes in apoptosis and the renin-angiotensin system (RAS) in fetal growth restriction (FGR).

MATERIALS AND METHOD

Fetuses were collected from patients who visited our hospital to either terminate or abort their pregnancy. Kidneys of fetuses which suffered with FGR, (n=11) at gestational age of 33.4±0.5 weeks and those from non-FGR (n=12) at gestational age of 34.3±0.9 weeks were collected. TUNEL, Bax and Bcl-2 staining were examined. The number of nephrons was also counted. Both protein and mRNA levels of renin and angiotensinogen were analyzed. Ultrasound was applied to measure fetus parameters including biparietal diameter, head circumference, circumference of abdomen, and femur length.

RESULTS

The number of nephrons was positively correlated with fetal weight at termination. Kidneys in the FGR group presented more apoptotic cells than those in the non-FGR group. Renin and angiotensinogen both decreased in the FGR group. Ultrasound revealed that biparietal diameter, abdomen circumference, femur length, and birth weight were all reduced in the FGR group compared with the non-FGR group. Kidney size was also restricted in the FGR group as indicated by ultrasound.

CONCLUSION

Renal apoptosis might contribute to the reduction of nephrons, and ultrasound plays a vital role in early diagnosis of developmental origins of health and disease (DOHAD).

Factors associated with a vicious cycle involving a low nephron number, hypertension and chronic kidney disease

It has been reported that there is substantial variation in the nephron number between individuals. Previous studies using autopsy kidneys have demonstrated that a low nephron number, in relation to a low birth weight, may result in hypertension (HTN) and/or chronic kidney disease (CKD). However, recent studies have revealed that the association between a low nephron number and HTN is not a universal finding. This observation indicates that a low nephron number is unlikely to be the sole factor contributing to an elevated blood pressure. In addition to the nephron number, various genetic and congenital factors may contribute to increased susceptibility to HTN and/or CKD in a complex manner. Acquired factors, including aging, obesity and related metabolic abnormalities, and various causes of renal injury, may additionally promote further nephron loss. Such a vicious cycle may induce HTN and/or CKD via the common mechanisms of renal hemodynamic maladaptation.

Fetal programming and cardiovascular pathology

Low birth weight serves as a crude proxy for impaired growth during fetal life and indicates a failure for the fetus to achieve its full growth potential. Low birth weight can occur in response to numerous etiologies that include complications during pregnancy, poor prenatal care, parental smoking, maternal alcohol consumption, or stress. Numerous epidemiological and experimental studies demonstrate that birth weight is inversely associated with blood pressure and coronary heart disease. Sex and age impact the developmental programming of hypertension. In addition, impaired growth during fetal life also programs enhanced vulnerability to a secondary insult. Macrosomia, which occurs in response to maternal obesity, diabetes, and excessive weight gain during gestation, is also associated with increased cardiovascular risk. Yet, the exact mechanisms that permanently change the structure, physiology, and endocrine health of an individual across their lifespan following altered growth during fetal life are not entirely clear. Transmission of increased risk from one generation to the next in the absence of an additional prenatal insult indicates an important role for epigenetic processes. Experimental studies also indicate that the sympathetic nervous system, the renin angiotensin system, increased production of oxidative stress, and increased endothelin play an important role in the developmental programming of blood pressure in later life. Thus, this review will highlight how adverse influences during fetal life and early development program an increased risk for cardiovascular disease including high blood pressure and provide an overview of the underlying mechanisms that contribute to the fetal origins of cardiovascular pathology.

Perinatally administered losartan augments renal ACE2 expression but not cardiac or renal Mas receptor in spontaneously hypertensive rats

Since the identification of the alternative angiotensin converting enzyme (ACE)2/Ang-(1-7)/Mas receptor axis, renin-angiotensin system (RAS) is a new complex target for a pharmacological intervention. We investigated the expression of RAS components in the heart and kidney during the development of hypertension and its perinatal treatment with losartan in young spontaneously hypertensive rats (SHR). Expressions of RAS genes were studied by the RT-PCR in the left ventricle and kidney of rats: normotensive Wistar, untreated SHR, SHR treated with losartan since perinatal period until week 9 of age (20 mg/kg/day) and SHR treated with losartan only until week 4 of age and discontinued until week 9. In the hypertrophied left ventricle of SHR, cardiac expressions of Ace and Mas were decreased while those of AT1 receptor (Agtr1a) and Ace2 were unchanged. Continuous losartan administration reduced LV weight (0.43 ± 0.02; P < 0.05 versus SHR) but did not influence altered cardiac RAS expression. Increased blood pressure in SHR (149 ± 2 in SHR versus 109 ± 2 mmHg in Wistar; P < 0.05) was associated with a lower renal expressions of renin, Agtr1a and Mas and with an increase in ACE2. Continuous losartan administration lowered blood pressure to control levels (105 ± 3 mmHg; P < 0.05 versus SHR), however, only renal renin and ACE2 were significantly up-regulated (for both P < 0.05 versus SHR). Conclusively, prevention of hypertension and LV hypertrophy development by losartan was unrelated to cardiac or renal expression of Mas. Increased renal Ace2, and its further increase by losartan suggests the influence of locally generated Ang-(1-7) in organ response to the developing hypertension in SHRs.

The Effect of Perinatal Taurine on Adult Renal Function Does Not Appear to Be Mediated by Taurine's Inhibition of the Renin-Angiotensin System

This study tests the hypothesis that perinatal taurine supplementation alters adult renal function by inhibition of the renin-angiotensin system. Female Sprague-Dawley rats were fed normal rat chow and given water alone (Control) or water containing an angiotensin converting enzyme inhibitor (captopril, 400 mg/ml) from conception until delivery (FD) or from delivery until weaning (LD). After weaning, the rats received normal rat chow and tap water. At 7–8 weeks of age, renal function at rest and after acute saline load was studied in conscious, restrained male rats. Body weight, mean arterial pressure, heart rate, effective renal blood flow, and renal vascular resistance were not significantly different among the three groups. Compared to Control, glomerular filtration rate, but not filtration fraction, significantly increased after saline load in both FD and LD groups. Water excretion significantly increased only in FD compared to Control, while fractional water excretion was significantly increased after saline load in both FD and LD groups. Sodium excretion significantly increased after saline load only in FD, while both captopril-treated groups significantly decreased fractional sodium excretion. Potassium excretion significantly increased in both FD and LD groups, while fractional potassium excretion significantly increased at rest in FD and decreased in LD groups after saline load. These effects of perinatal RAS inhibition on adult renal function contrast sharply, and are opposite in many cases to, the effects of perinatal taurine supplementation. Thus, these data suggest that perinatal taurine supplementation does not alter adult renal function through its ability to inhibit the perinatal RAS.

Genome-wide analysis of gestational gene-environment interactions in the developing kidney

The G protein-coupled bradykinin B2 receptor (Bdkrb2) plays an important role in regulation of blood pressure under conditions of excess salt intake. Our previous work has shown that Bdkrb2 also plays a developmental role since Bdkrb2(-/-) embryos, but not their wild-type or heterozygous littermates, are prone to renal dysgenesis in response to gestational high salt intake. Although impaired terminal differentiation and apoptosis are consistent findings in the Bdkrb2(-/-) mutant kidneys, the developmental pathways downstream of gene-environment interactions leading to the renal phenotype remain unknown. Here, we performed genome-wide transcriptional profiling on embryonic kidneys from salt-stressed Bdkrb2(+/+) and Bdkrb2(-/-) embryos. The results reveal significant alterations in key pathways regulating Wnt signaling, apoptosis, embryonic development, and cell-matrix interactions. In silico analysis reveal that nearly 12% of differentially regulated genes harbor one or more Pax2 DNA-binding sites in their promoter region. Further analysis shows that metanephric kidneys of salt-stressed Bdkrb2(-/-) have a significant downregulation of Pax2 gene expression. This was corroborated in Bdkrb2(-/-);Pax2(GFP+/tg) mice, demonstrating that Pax2 transcriptional activity is significantly repressed by gestational salt-Bdkrb2 interactions. We conclude that gestational gene (Bdkrb2) and environment (salt) interactions cooperate to impact gene expression programs in the developing kidney. Suppression of Pax2 likely contributes to the defects in epithelial survival, growth, and differentiation in salt-stressed BdkrB2(-/-) mice.

Sex differences in the developmental programming of hypertension

Experimental models of developmental programming provide proof of concept and support Barker's original findings that link birthweight and blood pressure. Many experimental models of developmental insult demonstrate a sex difference with male offspring exhibiting a higher blood pressure in young adulthood relative to their age-matched female counterparts. It is well recognized that men exhibit a higher blood pressure relative to age-matched women prior to menopause. Yet, whether this sex difference is noted in individuals born with low birthweight is not clear. Sex differences in the developmental programming of blood pressure may originate from innate sex-specific differences in expression of the renin angiotensin system that occur in response to adverse influences during early life. Sex differences in the developmental programming of blood pressure may also involve the influence of the hormonal milieu on regulatory systems key to the long-term control of blood pressure such as the renin angiotensin system in adulthood. In addition, the sex difference in blood pressure in offspring exposed to a developmental insult may involve innate sex differences in oxidative status or the endothelin system or may be influenced by age-dependent changes in the developmental programming of cardiovascular risk factors such as adiposity. Therefore, this review will highlight findings from different experimental models to provide the current state of knowledge related to the mechanisms that contribute to the aetiology of sex differences in the developmental programming of blood pressure and hypertension.

Maternal high-fat diet programs rat offspring hypertension and activates the adipose renin-angiotensin system

OBJECTIVE

A maternal high-fat diet creates an increased risk of offspring obesity and systemic hypertension. Although the renal renin-angiotensin system (RAS) is known to regulate blood pressure, it is now recognized that the RAS is also activated in adipose tissue during obesity. We hypothesized that programmed offspring hypertension is associated with the activation of the adipose tissue RAS in the offspring of obese rat dams.

STUDY DESIGN

At 3 weeks of age, female rats were weaned to a high-fat diet (60% k/cal; n = 6) or control diet (10% k/cal; n = 6). At 11 weeks of age, these rats were mated and continued on their respective diets during pregnancy. After birth, at 1 day of age, subcutaneous adipose tissue was collected; litter size was standardized, and pups were cross-fostered to either control or high-fat diet dams, which created 4 study groups. At 21 days of age, offspring were weaned to control or high-fat diet. At 6 months of age, body fat and blood pressure were measured. Thereafter, subcutaneous and retroperitoneal adipose tissue was harvested from male offspring. Protein expression of adipose tissue RAS components were determined by Western blotting.

RESULTS

The maternal high-fat diet induced early and persistent alterations in offspring adipose RAS components. These changes were dependent on the period of exposure to the maternal high-fat diet, were adipose tissue specific (subcutaneous and retroperitoneal), and were exacerbated by a postnatal high-fat diet. Maternal high-fat diet increased adiposity and blood pressure in offspring, regardless of the period of exposure.

CONCLUSION

These findings suggest that programmed adiposity and the activation of the adipose tissue RAS are associated with hypertension in offspring of obese dams.

High-salt diets during pregnancy affected fetal and offspring renal renin-angiotensin system

Intrauterine environments are related to fetal renal development and postnatal health. Influence of salty diets during pregnancy on renal functions and renin-angiotensin system (RAS) was determined in the ovine fetuses and offspring. Pregnant ewes were fed high-salt diet (HSD) or normal-salt diet (NSD) for 2 months during middle-to-late gestation. Fetal renal functions, plasma hormones, and mRNA and protein expressions of the key elements of renal RAS were measured in the fetuses and offspring. Fetal renal excretion of sodium was increased while urine volume decreased in the HSD group. Fetal blood urea nitrogen was increased, while kidney weight:body weight ratio decreased in the HSD group. The altered ratio was also observed in the offspring aged 15 and 90 days. Maternal and fetal plasma antidiuretic hormone was elevated without changes in plasma renin activity and Ang I levels, while plasma Ang II was decreased. The key elements of local renal RAS, including angiotensinogen, angiotensin converting enzyme (ACE), ACE2, AT1, and AT2 receptor expression in both mRNA and protein, except renin, were altered following maternal high salt intake. The results suggest that high intake of salt during pregnancy affected fetal renal development associated with an altered expression of the renal key elements of RAS, some alterations of fetal origins remained after birth as possible risks in developing renal or cardiovascular diseases.

Fetal hypoxia results in programming of aberrant angiotensin ii receptor expression patterns and kidney development

AIMS

The present study tested the hypothesis that fetal hypoxia adversely affects kidney development in fetal and offspring rats and alter the expression patterns of angiotensin II type 1 (AT1R) and type 2 (AT2R) receptors.

METHODS

Time-dated pregnant rats were divided between normoxic and hypoxic (10.5% O2 last period of gestation) groups. Protein expression, in the offspring, was determined using western blot.

RESULTS

Hypoxic treatment significantly decreased body and kidney weight in 21-day fetuses (E21) and 7-day neonates (P7). In 3-month-old offspring there were no significant differences in body and kidney weight between hypoxic and control animals. Fetal hypoxia had no effect on kidney AT1R density in E21 or P7, but significantly decreased kidney AT1R protein and mRNA abundance in both male and female adults. In contrast, kidney AT2R density was not affected by fetal hypoxia throughout the developmental stages studied. The hypoxia-mediated reduction of nephron numbers was progressively from P7 worsened into the adulthood with females affected more than males.

CONCLUSION

The results suggest that fetal hypoxia causes programming of aberrant kidney development and accelerates the aging process of the kidney during the postnatal development, which may contribute to an increased risk of cardiovascular disease.

Safety in glomerular numbers

A low nephron number is, according to Brenner's hyperfiltration hypothesis, associated with hypertension, glomerular damage and proteinuria, and starts a vicious cycle that ends in renal failure over the long term. Nephron endowment is set during foetal life, and there is no formation of nephrons after 34-36 weeks of gestation, indicating that many factors before that time-point may have an impact on kidney development and reduce nephron numbers. Such factors include maternal malnutrition, stress, diseases, such as diabetes, uteroplacental insufficiency, maternal and neonatal drugs and premature birth. However, other congenital anomalies, such as renal hypoplasia, unilateral renal agenesis or multicystic dysplastic kidney, may also lead to a reduced nephron endowment, with an increased risk for hypertension, renal dysfunction and the need for renal replacement therapy. This review focuses on the causes and consequences of a low nephron endowment and will illustrate why there is safety in glomerular numbers.

Metabolic programming during lactation stimulates renal Na+ transport in the adult offspring due to an early impact on local angiotensin II pathways

Background

Several studies have correlated perinatal malnutrition with diseases in adulthood, giving support to the programming hypothesis. In this study, the effects of maternal undernutrition during lactation on renal Na⁺-transporters and on the local angiotensin II (Ang II) signaling cascade in rats were investigated.

Methodology/Principal Findings

Female rats received a hypoproteic diet (8% protein) throughout lactation. Control and programmed offspring consumed a diet containing 20% protein after weaning. Programming caused a decrease in the number of nephrons (35%), in the area of the Bowman's capsule (30%) and the capillary tuft (30%), and increased collagen deposition in the cortex and medulla (by 175% and 700%, respectively). In programmed rats the expression of (Na⁺+K⁺)ATPase in proximal tubules increased by 40%, but its activity was doubled owing to a threefold increase in affinity for K⁺. Programming doubled the ouabain-insensitive Na⁺-ATPase activity with loss of its physiological response to Ang II, increased the expression of AT₁ and decreased the expression of AT₂ receptors), and caused a pronounced inhibition (90%) of protein kinase C activity with decrease in the expression of the α (24%) and ε (13%) isoforms. Activity and expression of cyclic AMP-dependent protein kinase decreased in the same proportion as the AT₂ receptors (30%). In vivo studies at 60 days revealed an increased glomerular filtration rate (GFR) (70%), increased Na⁺ excretion (80%) and intense proteinuria (increase of 400% in protein excretion). Programmed rats, which had normal arterial pressure at 60 days, became hypertensive by 150 days.

Conclusions/Significance

Maternal protein restriction during lactation results in alterations in GFR, renal Na⁺ handling and in components of the Ang II-linked regulatory pathway of renal Na⁺ reabsorption. At the molecular level, they provide a framework for understanding how metabolic programming of renal mechanisms contributes to the onset of hypertension in adulthood.

Both high and low maternal salt intake in pregnancy alter kidney development in the offspring

In humans, low glomerular numbers are related to hypertension, cardiovascular, and renal disease in adult life. The present study was designed 1) to explore whether above- or below-normal dietary salt intake during pregnancy influences nephron number and blood pressure in the offspring and 2) to identify potential mechanisms in kidney development modified by maternal sodium intake. Sprague-Dawley rats were fed low (0.07%)-, intermediate (0.51%)-, or high (3.0%)-sodium diets during pregnancy and lactation. The offspring were weaned at 4 wk and subsequently kept on a 0.51% sodium diet. The kidney structure was assessed at postnatal weeks 1 and 12 and the expression of proteins of interest at term and at week 1. Blood pressure was measured in male offspring by telemetry from postnatal month 2 to postnatal month 9. The numbers of glomeruli at weeks 1 and 12 were significantly lower and, in males, telemetrically measured mean arterial blood pressure after month 5 was higher in offspring of dams on a high- or low- compared with intermediate-sodium diet. A high-salt diet was paralleled by higher concentrations of marinobufagenin in the amniotic fluid and an increase in the expression of both sprouty-1 and glial cell-derived neutrophic factor in the offspring's kidney. The expression of FGF-10 was lower in offspring of dams on a low-sodium diet, and the expression of Pax-2 and FGF-2 was lower in offspring of dams on a high-sodium diet. Both excessively high and excessively low sodium intakes during pregnancy modify protein expression in offspring kidneys and reduce the final number of glomeruli, predisposing the risk of hypertension later in life.

Maternal smoking during pregnancy and kidney volume in the offspring: the Generation R Study

An adverse fetal environment leads to smaller kidneys, with fewer nephrons, which might predispose an individual to the development of kidney disease and hypertension in adult life. In a prospective cohort study among 1,072 children followed from early fetal life onward, we examined whether maternal smoking during pregnancy, as a significant adverse fetal exposure, is associated with fetal (third trimester of pregnancy, n = 1,031) and infant kidney volume (2 years of age, n = 538) measured by ultrasound. Analyses were adjusted for various potential confounders. Among mothers who continued smoking, we observed dose-dependent associations between the number of cigarettes smoked during pregnancy and kidney volume in fetal life. Smoking less than five cigarettes per day was associated with larger fetal combined kidney volume, while smoking more than ten cigarettes per day tended to be associated with smaller fetal combined kidney volume (p for trend: 0.002). This pattern was not significant for kidney volume at the age of 2 years. Our results suggest that smoking during pregnancy might affect kidney development in fetal life with a dose-dependent relationship. Further studies are needed to assess the underlying mechanisms and whether these differences in fetal kidney volume have postnatal consequences for kidney function and blood pressure.

Renal programming: cause for concern?

Development of the kidney can be altered in utero in response to a suboptimal environment. The intrarenal factors that have been most well characterized as being sensitive to programming events are kidney mass/nephron endowment, the renin-angiotensin system, tubular sodium handling, and the renal sympathetic nerves. Newborns that have been subjected to an adverse intrauterine environment may thus begin life at a distinct disadvantage, in terms of renal function, at a time when the kidney must take over the primary role for extracellular fluid homeostasis from the placenta. A poor beginning, causing renal programming, has been linked to increased risk of hypertension and renal disease in adulthood. However, although a cause for concern, increasingly, evidence demonstrates that renal programming is not a fait accompli in terms of future cardiovascular and renal disease. A greater understanding of postnatal renal maturation and the impact of secondary factors (genes, sex, diet, stress, and disease) on this process is required to predict which babies are at risk of increased cardiovascular and renal disease as adults and to be able to devise preventative measures.

Castration fails to prevent prenatally programmed hypertension in male rats

Male offspring of rats that were modestly protein restricted during pregnancy become hypertensive as adults, whereas their female littermates remain normotensive. The purpose of this study was to determine the role of testosterone in promoting this sexual dimorphism of prenatally programmed hypertension. Rats were fed either a normal (19% protein, NP) or modestly protein-restricted (8.5% protein, LP) diet throughout pregnancy. Male offspring either remained intact or were castrated (CAS) at 30 days of age. Female offspring remained intact. At approximately 22 wk of age, the offspring were chronically instrumented for measurement of mean arterial pressure and renal function. Intact male LP offspring were hypertensive compared with male NP offspring (138 +/- 2 vs. 130 +/- 2 mmHg, P < 0.007), whereas female LP offspring were normotensive (123 +/- 1 vs. 122 +/- 2 mmHg in NP females). In CAS males, blood pressure in both diet groups was not different from that in intact males of the same group (138 +/- 3 mmHg in LP CAS males, and 131 +/- 2 mmHg in NP CAS males). Glomerular filtration rate and effective renal plasma flow were also not significantly affected by castration. However, castration significantly reduced protein excretion in LP males to levels not different from those in NP CAS and intact males. Renal histopathology scores showed a similar pattern. Thus removal of androgens by castration failed to provide any protective effect against the hypertension programmed by maternal protein restriction. Castration also failed to abolish the sex difference in blood pressure in both diet groups. These findings suggest that the lifelong presence of normal levels of testicular hormones does not play a major role either in maintaining baseline blood pressure higher in males than in females, or in promoting further elevations in blood pressure in males due to prenatal undernutrition. However, androgens such as testosterone may promote renal injury in LP males.

Angiotensin II promotes development of the renal microcirculation through AT1 receptors

Pharmacologic or genetic deletion of components of the renin-angiotensin system leads to postnatal kidney injury, but the roles of these components in kidney development are unknown. To test the hypothesis that angiotensin II supports angiogenesis during postnatal kidney development, we quantified CD31(+) postglomerular microvessels, performed quantitative PCR analysis of vascular growth factor expression, and measured renal blood flow by magnetic resonance. Treating rats with the angiotensin II type 1 receptor antagonist candesartan for 2 weeks after birth reduced the total length, volume, and surface area of capillaries in both the cortex and the medulla and inhibited the organization of vasa recta bundles. In addition, angiotensin II type 1 antagonism inhibited the transcription of angiogenic growth factors vascular endothelial growth factor, angiopoietin-1, angiopoietin-2, and the angiopoietin receptor Tie-2 in cortex and medulla. Similarly, Agtr1a(-/-);Agtr1b(-/-) mouse kidneys had decreased angiopoietin-1, angiopoietin-2, and Tie-2 mRNAs at postnatal day 14. To test whether increased urinary flow leads to microvascular injury, we induced postnatal polyuria with either lithium or adrenalectomy, but these did not alter vascular endothelial growth factor expression or vasa recta organization. Compared with vehicle-treated rats, renal blood flow was significantly (approximately 20%) lower in candesartan-treated rats even 14 days after candesartan withdrawal. Taken together, these data demonstrate that angiotensin II promotes postnatal expansion of postglomerular capillaries and organization of vasa recta bundles, which are necessary for development of normal renal blood flow.

Role of fetal programming in the development of hypertension

Epidemiological studies have suggested that size at birth contributes to increased cardiovascular disease (CVD) risk in later life. Findings from experimental studies are providing insight into the mechanisms linking impaired fetal growth and the increased risk of CVD and hypertension in adulthood. This article summarizes potential mechanisms involved in the fetal programming of hypertension and CVD, including alterations in the organs and regulatory systems critical to long-term control of sodium and volume homeostasis.

Role of the kidney in the prenatal and early postnatal programming of hypertension

Epidemiologic studies from several different populations have demonstrated that prenatal insults, which adversely affect fetal growth, result in an increased incidence of hypertension when the offspring reaches adulthood. It is now becoming evident that low-birth-weight infants are also at increased risk for chronic kidney disease. To determine how prenatal insults result in hypertension and chronic kidney disease, investigators have used animal models that mimic the adverse events that occur in pregnant women, such as dietary protein or total caloric deprivation, uteroplacental insufficiency, and prenatal administration of glucocorticoids. This review examines the role of the kidney in generating and maintaining an increase in blood pressure in these animal models. This review also discusses how early postnatal adverse events may have repercussions in later life. Causes for the increase in blood pressure by perinatal insults are likely multifactorial and involve a reduction in nephron number, dysregulation of the systemic and intrarenal renin-angiotensin system, increased renal sympathetic nerve activity, and increased tubular sodium transport. Understanding the mechanism for the increase in blood pressure and renal injury resulting from prenatal insults may lead to therapies that prevent hypertension and the development of chronic kidney and cardiovascular disease.

Children's toxicology from bench to bed--Drug-induced renal injury (1): The toxic effects of ARB/ACEI on fetal kidney development

Development of fetal kidney is a finely programmed sequence, and is regulated by many important molecules. The perturbation of normal kidney development leads to congenital anomalies of kidney and urinary tract (CAKUT). CAKUT includes hypoplastic/dysplastic kidney, obstructive nephropathy and several other anomalies. CAKUT is of clinically importance, since it could lead to end stage renal failure when its anomaly grade is severe. So far, several causative genes responsible for development of CAKUT have been identified, including genes encoding molecules related to the renin-angiotensin-aldosterone system, RAS system. In humans, maternal administration of agents with inhibitory effects on the RAS system, such as angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin type 1 receptor blockers (ARBs), have been reported to cause severe renal malformation, designated as ACEI/ARB fetopathy. In this paper, we overview the development of fetal kidney and address the effects of ACEIs/ARBs on fetal kidney.

Salt-losing nephrogenic diabetes insipidus caused by fetal exposure to angiotensin receptor blocker

The administration of angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin type 1 receptor blockers (ARBs) to pregnant women has been reported to cause ACEI/ARB fetopathy, including oligohydramios, pulmonary hypoplasia, renal insufficiency, limb contracture, and fetal hypotension in the child. Most of the patients die or develop end-stage renal failure during the neonatal period. The long-term prognosis of renal dysfunctions of patients with ARB fetopathy has not been reported. We report two pediatric cases, a 6- and 2-year-old boy, respectively, with ARB fetopathy whose renal functions were thoroughly evaluated after recovery from neonatal renal failure. Both patients showed (1) mildly decreased glomerular filtration rate, (2) no significant proximal tubular dysfunctions, and (3) salt-losing nephrogenic diabetes insipidus, while the excretion of arginine vasopressin and urine level of cyclic AMP were increased. The data on these two patients indicate that the administration of ARB to the fetus profoundly impairs the urine concentrating ability, probably due to papillary atrophy and the disturbed formation of the osmotic gradient in the medulla, which have been confirmed in neonatal rats administered with ACEIs or ARBs. ACEIs/ARBs must not be administered to pregnant women.

Plasma and renal renin concentrations in adult sheep after prenatal betamethasone exposure

This study examined whether renin expression and secretion and plasma angiotensin II (Ang II) levels were altered in adult sheep exposed to antenatal betamethasone. Pregnant sheep received injections of 0.17 mg/kg betamethasone or vehicle, at 80 and 81 days of gestation, and offspring were studied at 6 and 18 months of age. At 6 months, plasma prorenin concentrations were significantly lower in betamethasone animals (4.63 +/- 0.64 vs 7.09 +/- 0.83 ng angiotensin I/mL/h, P < .01). The percentage of plasma active renin was significantly higher in the betamethasone group (31.93 +/- 4.09% vs 18.57 +/- 2.79%, P < .01). Plasma and renocortical renin levels were similar in both groups at 18 months, but plasma renin activity was lower than at 6 months. Ang II levels were suppressed by betamethasone. The data indicate that prenatal exposure to betamethasone alters processing and secretion of renin in offspring at 6 months, but that this difference is not apparent at 18 months.

Gender differences in the effects of antenatal betamethasone exposure on renal function in adult sheep

Exposure to clinically relevant doses of glucocorticoids during fetal life increases blood pressure in adult male and female sheep. The purpose of this study was to evaluate the effects of prenatal exposure to betamethasone at 80-81 days of gestation on renal function in ewes and rams at 1.5 yr of age. In prenatal betamethasone-exposed males, compared with the vehicle-exposed animals, basal glomerular filtration rate (GFR) (1.93 +/- 0.08 vs. 2.27 +/- 0.10 ml.min(-1).kg body wt(-1)) and the ability to excrete an acute Na+ load (37.1 +/- 4.4 vs. 53.7 +/- 9.7%) were reduced. (P < 0.03 and P = 0.03, respectively). In contrast, prenatal betamethasone exposure had no effect on basal GFR, Na+ excretion, or the percentage of the Na+ load excreted during the experiment in females. Systemic infusions of ANG-(1-7) at 9 ng.min(-1).kg(-1) for 2 h had minimal effects on basal GFR, renal plasma flow, and Na+ excretion in males but increased Na+ excretion in females. However, the percentage of Na+ load excreted during ANG-(1-7) infusion did not change in prenatal betamethasone-exposed females (113.1 +/- 14.2 vs. 98.1 +/- 12.2%) compared with the significant increase in vehicle females (139.2 +/- 22.3 vs. 92.2 +/- 7.5%) (P = 0.01). The data indicate that antenatal betamethasone exposure produces gender-specific alternations in renal function and thus suggest that different mechanisms underlie the antenatal steroid-induced elevations in blood pressure in male and female offspring.

Sex differences in the developmental origins of hypertension and cardiorenal disease

The "developmental origins of health and disease" (DOHAD) hypothesis derives from clinical observations, indicating long-term health consequences for persons of low birth weight. There is growing evidence, primarily from animal studies, that supports the idea that processes put in motion during development that contribute to DOHAD do not necessarily reflect as significantly compromised growth and altered birth weight. Throughout the body of work investigating the DOHAD hypothesis, several themes have emerged; the importance of the placenta, the presence of critical periods of vulnerability, the involvement of the kidney in programmed hypertension, the presence of sex differences in the progression and development of adult diseases. Despite compelling findings in recent studies, much remains unclear regarding the impact of biological sex in the progression of human diseases, in general, and in the mechanisms underlying developmentally programmed responses, in particular. Although the contribution of biological sex to DOHAD is increasingly recognized, it also appears that it may exert distinctly different influences during fetal and adult life. The mechanisms by which biological sex contributes to these processes remains nebulous at present; nevertheless, several intriguing mechanistic candidates have been proposed ranging from differences in the amounts of sex hormones (e.g., estrogens, androgens) to recently described sexual dimorphism in the transcriptome of a variety of mammalian tissues. Recognizing the influences of biological sex or sex hormones on DOHAD uniquely situates research in this area to provide significant insights into the development and progression of many diseases, recent examples of which are the subject of this review.

Alterations in circulatory and renal angiotensin-converting enzyme and angiotensin-converting enzyme 2 in fetal programmed hypertension

Antenatal betamethasone treatment is a widely accepted therapy to accelerate lung development and improve survival in preterm infants. However, there are reports that infants who receive antenatal glucocorticoids exhibit higher systolic blood pressure in their early adolescent years. We have developed an experimental model of programming whereby the offspring of pregnant sheep administered clinically relevant doses of betamethasone exhibit elevated blood pressure. We tested the hypothesis as to whether alterations in angiotensin-converting enzyme (ACE), ACE2, and neprilysin in serum, urine, and proximal tubules are associated with this increase in mean arterial pressure. Male sheep were administered betamethasone (2 doses of 0.17 mg/kg, 24 hours apart) or vehicle at the 80th day of gestation and delivered at term. Sheep were instrumented at adulthood (1.8 years) for direct conscious recording of mean arterial pressure. Serum and urine were collected and proximal tubules isolated from the renal cortex. Betamethasone-treated animals had elevated mean arterial pressure (97+/-3 versus 83+/-2 mm Hg; P<0.05) and a 25% increase in serum ACE activity (48.4+/-7.0 versus 36.0+/-2.7 fmol/mL per minute) but a 40% reduction in serum ACE2 activity (18.8+/-1.2 versus 31.4+/-4.4 fmol/mL per minute). In isolated proximal tubules, ACE2 activity and expression were 50% lower in the treated sheep with no significant change in ACE or neprilysin activities. We conclude that antenatal steroid treatment results in the chronic alteration of ACE and ACE2 in the circulatory and tubular compartments, which may contribute to the higher blood pressure in this model of fetal programming-induced hypertension.

Sex differences in the fetal programming of hypertension

BACKGROUND

Numerous clinical and experimental studies support the hypothesis that the intrauterine environment is an important determinant of cardiovascular disease and hypertension.

OBJECTIVE

This review examined the mechanisms linking an adverse fetal environment and increased risk for chronic disease in adulthood with an emphasis on gender differences and the role of sex hormones in mediating sexual dimorphism in response to a suboptimal fetal environment.

METHODS

This review focuses on current findings from the PubMed database regarding animal models of fetal programming of hypertension, sex differences in phenotypic outcomes, and potential mechanisms in offspring of mothers exposed to an adverse insult during gestation. For the years 1988 to 2007, the database was searched using the following terms: fetal programming, intrauterine growth restriction, low birth weight, sex differences, estradiol, testosterone, high blood pressure, and hypertension.

RESULTS

The mechanisms involved in the fetal programming of adult disease are multifactorial and include alterations in the regulatory systems affecting the long-tterm control of arterial pressure. Sex differences have been observed in animal models of fetal programming, and recent studies suggest that sex hormones may modulate activity of regulatory systems, leading to a lower incidence of hypertension and vascular dysfunction in females compared with males.

CONCLUSIONS

Animal models of fetal programming provide critical support for the inverse relationship between birth weight and blood pressure. Experimental models demonstrate that sex differences are observed in the pathophysiologic response to an adverse fetal environment. A role for sex hormone involvement is strongly suggested,with modulation of the renin-angiotensin system as a possible mechanism.

Moderate zinc restriction during fetal and postnatal growth of rats: effects on adult arterial blood pressure and kidney

Intrauterine and postnatal zinc restriction may result in an adverse environment for the development of cardiovascular and renal systems. This study evaluated the effects of moderate zinc deficiency during fetal life, lactation, and/or postweaning growth on systolic blood pressure, renal function, and morphology in adult life. Female Wistar rats received low (8 ppm) or control (30 ppm) zinc diets from the beginning of pregnancy up to weaning. After weaning, male offspring of each group of mothers were fed low or control zinc diet. Systolic blood pressure, creatinine clearance, proteinuria, renal morphology, renal apoptosis. and renal oxidative stress state were evaluated after 60 days. Zinc deficiency during pre- and postweaning growth induced an increase in systolic blood pressure and a decrease in the glomerular filtration rate associated with a reduction in the number and size of nephrons. Activation of renal apoptosis, reduction in catalase activity, glutathione peroxidase activity, and glutathione levels and increase in lipid peroxidation end products could explain these morphometric changes. Zinc deficiency through pre- and postweaning growth induced more pronounced renal alteration than postweaning zinc deficiency. These animals showed signs of renal fibrosis, proteinuria, increased renal apoptosis, and higher lipid peroxidation end products. A control diet during postweaning growth did not totally overcome renal oxidative stress damage, apoptosis, and fibrosis induced by zinc deficiency before weaning. In conclusion, zinc deficiency during a critical period of renal development and maturation could induce functional and morphological alterations that result in elevated blood pressure and renal dysfunction in adult life.

Differential effects of maternal nutrient restriction through pregnancy on kidney development and later blood pressure control in the resulting offspring

The mechanisms whereby maternal nutritional manipulation through pregnancy result in altered blood pressure in the offspring may include changes in fetal and newborn and adult renal prostaglandin (PG) synthesis, metabolism, and receptor expression. Since the postnatal effects of nutrient restriction on the renal PG synthesis and receptor system during nephrogenesis in conjunction with nephron numbers and blood pressure have not been evaluated in the rat, the present study examined the effect of reducing maternal food intake by 50% of ad libitum through pregnancy on young male rats. Six control-fed mothers and eight nutrient-restricted pregnant rats with single litter mates were used at each sampling time point, most of which occurred during nephrogenesis. Offspring of nutrient-restricted dams were lighter from birth to 3 days. This was accompanied by reduced PGE2, with smaller kidneys up to 14 days. Nutrient restriction also decreased mRNA expression of the PG synthesis enzyme, had little effect on the PG receptors, and increased mRNA expression of the degradation enzyme during nephrogenesis and the glucocorticoid receptor in the adult kidney. These mRNA changes were normally accompanied by similar changes in protein. Nephron number was also reduced from 7 days up to adulthood when blood pressure (measured by telemetry) did not increase as much as in control offspring during the dark, active period. In conclusion, maternal nutrient restriction suppressed renal PG concentrations in the offspring, and this was associated with suppressed kidney growth and development and decreased blood pressure.

AT1 blockade during lactation as a model of chronic nephropathy: mechanisms of renal injury

Suppression of the renin-angiotensin system during lactation causes irreversible renal structural changes. In this study we investigated 1) the time course and the mechanisms underlying the chronic kidney disease caused by administration of the AT(1) receptor blocker losartan during lactation, and 2) whether this untoward effect can be used to engender a new model of chronic kidney disease. Male Munich-Wistar pups were divided into two groups: C, whose mothers were untreated, and L(Lact), whose mothers received oral losartan (250 mg.kg(-1).day(-1)) during the first 20 days after delivery. At 3 mo of life, both nephron number and the glomerular filtration rate were reduced in L(Lact) rats, whereas glomerular pressure was elevated. Unselective proteinuria and decreased expression of the zonula occludens-1 protein were also observed, along with modest glomerulosclerosis, significant interstitial expansion and inflammation, and wide glomerular volume variation, with a stable subpopulation of exceedingly small glomeruli. In addition, the urine osmolality was persistently lower in L(Lact) rats. At 10 mo of age, L(Lact) rats exhibited systemic hypertension, heavy albuminuria, substantial glomerulosclerosis, severe renal interstitial expansion and inflammation, and creatinine retention. Conclusions are that 1) oral losartan during lactation can be used as a simple and easily reproducible model of chronic kidney disease in adult life, associated with low mortality and no arterial hypertension until advanced stages; and 2) the mechanisms involved in the progression of renal injury in this model include glomerular hypertension, glomerular hypertrophy, podocyte injury, and interstitial inflammation.

Intrauterine growth restriction: fetal programming of hypertension and kidney disease

The etiology of hypertension historically includes 2 components: genetics and lifestyle. However, recent epidemiologic studies report an inverse relationship between birth weight and hypertension suggesting that a suboptimal fetal environment may also contribute to increased disease in later life. Experimental studies support this observation and indicate that cardiovascular/kidney disease originates in response to fetal adaptations to adverse conditions during prenatal life.

Vitamin D deficiency during pregnancy and lactation stimulates nephrogenesis in rat offspring

There is increasing evidence of vitamin D insufficiency in women of child-bearing age and their infants. This study examined the effect of maternal vitamin D deficiency on nephron endowment in rat offspring (n=7 per group). Sprague-Dawley dams were fed either a vitamin D deplete diet or a vitamin replete (control) diet prior to pregnancy, during pregnancy and throughout lactation. At 4 weeks of age the offspring were weaned and maintained on their respective diets until they were killed at 7 weeks. In the fixed right kidney, kidney volume, renal corpuscle volume and nephron number were stereologically determined. There was no difference between groups in body weight, kidney weight or kidney volume. There was a significant 20% increase in nephron number in kidneys of vitamin D deplete offspring (vitamin D deficient, 29,000+/-1,858, control, 23,330+/-1,828; P=0.04). This was accompanied by a significant decrease in renal corpuscle size in the vitamin D deplete group compared with the controls (6.125+/-0.576 x 10(-4) mm(3) and 8.178+/-0.247 x 10(-4) mm(3), respectively; P=0.03). We concluded that maternal vitamin D deficiency in rats appears to stimulate nephrogenesis. Whether this confers a renal functional advantage or not is unknown.

Effects of early postnatal hypernutrition on nephron number and long-term renal function and structure in rats

Various antenatal events impair nephrogenesis in humans as well as in several animal models. The consecutive low nephron endowment may contribute to an increased risk for cardiovascular and renal diseases in adulthood. However, little knowledge is available on the influence of the postnatal environment, especially nutrition, on nephrogenesis. Moreover, the consequences of early postnatal nutrition in late adulthood are not clear. We used a model of early postnatal overfeeding (OF) induced by reduction of litter size (3 pups/litter) in rats. Systolic blood pressure (SBP; plethysmography), glomerular filtration rate (clearance of creatinine), glomerular number and volume, and glomerulosclerosis were evaluated in 22-mo-old aging offspring. Early postnatal OF was associated with increased weight gain during the suckling period (+40%, P < 0.01) and a 20% increase in glomerular number (P < 0.05). However, an increase in SBP at 12 mo by an average of 18 mmHg and an increase in proteinuria (2.6-fold) and glomerulosclerosis at 22 mo of age were observed in OF male offspring compared with controls. In conclusion, early postnatal OF in the rat enhances postnatal nephrogenesis, but elevated blood pressure and glomerulosclerosis are still observed in male adults. Factors other than glomerular number reduction are likely to contribute to the arterial hypertension induced by early postnatal OF.

Maternal undernutrition inhibits angiogenesis in the offspring: a potential mechanism of programmed hypertension

The underlying etiology of many chronic diseases such as hypertension and diabetes has been traced to the in utero environment. Our interest has focused on determining the mechanism of programmed hypertension. In our rodent model of 50% maternal food restriction (MFR) from day 10 of gestation to term, the offspring develop hypertension as adults. We hypothesized that maternal undernutrition inhibits angiogenesis such that the neonate is endowed with fewer microvessels, increasing their susceptibility to develop hypertension as adults. We found significantly reduced number of mesenteric branching and renal medullary microvessels in the 1-day-old MFR newborns. Endothelial cells from MFR offspring generated shorter neovessels in culture compared with controls. The inhibition of angiogenesis was associated with a significant decrease in VEGF protein expression in mesenteric microvessels and aortas in 1-day-old offspring. However, in adulthood there was a marked increase in VEGF expression in both vessel types. The expression of endothelial nitric oxide synthase protein was also found to be increased in both renal and mesenteric microvessels and in aortas in the 1-day-old MFR offspring. These results suggest that MFR results in inhibition of VEGF expression in microvascular and aortic endothelial cells early in life, resulting in decreased angiogenesis and increased peripheral vascular resistance, both of which may contribute to offspring hypertension.

Placental insufficiency results in temporal alterations in the renin angiotensin system in male hypertensive growth restricted offspring

Reduced uterine perfusion initiated in late gestation in the rat results in intrauterine growth restriction (IUGR) and development of hypertension by 4 wk of age. We hypothesize that the renin angiotensin system (RAS), a regulatory system important in the long-term control of blood pressure, may be programmed by placental insufficiency and may contribute to the etiology of IUGR hypertension. We previously reported that RAS blockade abolished hypertension in adult IUGR offspring; however, the mechanisms responsible for the early phase of hypertension are unresolved. Therefore, the purpose of this study was to examine RAS involvement in early programmed hypertension and to determine whether temporal changes in RAS expression are observed in IUGR offspring. Renal renin and angiotensinogen mRNA expression were significantly decreased at birth (80 and 60%, respectively); plasma and renal RAS did not differ in conjunction with hypertension (mean increase of 14 mmHg) in young IUGR offspring; however, hypertension (mean increase of 22 mmHg) in adult IUGR offspring was associated with marked increases in renal angiotensin-converting enzyme (ACE) activity (122%) and renal renin and angiotensinogen mRNA (7-fold and 7.4-fold, respectively), but no change in renal ANG II or angiotensin type 1 receptor. ACE inhibition (enalapril, 10 mg x kg(-1) x day(-1), administered from 2 to 4 wk of age) abolished hypertension in IUGR at 4 wk of age (decrease of 15 mmHg, respectively) with no significant depressor effect in control offspring. Therefore, temporal alterations in renal RAS are observed in IUGR offspring and may play a key role in the etiology of IUGR hypertension.

Sex and age differences of renal function in rats with reduced ANG II activity during the nephrogenic period

This study was designed to test the hypothesis that blockade of angiotensin II effects during renal development accelerates the aging-related changes in renal hemodynamics and proteinuria, and that these changes are sex dependent. It has also been examined whether the deterioration of urinary concentrating ability elicited by angiotensin II blockade is sex and/or aging dependent. Newborn Sprague-Dawley rats were treated with vehicle or an AT(1) angiotensin II receptor antagonist (ARA) during the first 14 postnatal days. Blood pressure, glomerular filtration rate, proteinuria, and urinary concentrating ability in response to dehydration were examined in conscious rats at 3 and 11 mo of age. ARA treatment elicited a similar increment in blood pressure in males and females that was greater (P < 0.05) at 11 than at 3 mo of age. Glomerular filtration rate only decreased (P < 0.05) in 11-mo-old male ARA-treated rats (0.59 +/- 0.07 vs. 0.80 +/- 0.07 ml.min(-1).g(-1) in control group). At 3 mo of age, proteinuria increased in male (107%) but not in female ARA-treated rats. However, at 11 mo of age, proteinuria increased in both sexes, but the increment was greater (P < 0.05) in male (244%) than in female (138%) ARA-treated rats. Renal ability to concentrate urine in response to prolonged water dehydration was only reduced in ARA-treated males. The reduction of urinary concentrating ability was accentuated by aging. Therefore, we conclude that blockade of angiotensin II effects during renal development elicits an important deterioration of cortical and medullary function that is sex and aging dependent.

Prenatal corticosterone exposure results in altered AT1/AT2, nephron deficit and hypertension in the rat offspring

Maternal treatment with the synthetic glucocorticoid, dexamethasone has been reported to result in a nephron deficit and development of hypertension in the offspring of rats. However, it is not known whether elevated maternal corticosterone (CORT), the natural glucocorticoid, has similar effects on blood pressure and nephron endowment. The present study investigated the effects of CORT (0.8 mg kg(-1) day(-1)) administration on embryonic day 14 (E14) and E15 of pregnancy on: (1) nephron number at postnatal day 30 (PN30); (2) blood pressure at PN120; and (3) receptors of the renal renin-angiotensin system (RRAS) (AT(1)Ra, AT(1)Rb and AT(2)Ra) during both embryonic (E16, E20) and adolescent (PN30) life. Plasma CORT concentrations were approximately doubled 30 min after injection. Unbiased stereological analysis revealed that maternal CORT treatment resulted in a nephron deficit of 21 and 19% in male and female offspring, respectively. Mean arterial pressures were significantly elevated in offspring of both sexes from the CORT group. Real-time PCR revealed that CORT treatment increased expression of AT(1)Ra and AT(2)R at E16, and at PN30. Expression of AT(1)Rb was downregulated in embryonic life but upregulated at PN30. We believe that these results are the first to demonstrate that maternal CORT treatment results in a nephron deficit and development of hypertension in the rat offspring. Changes in the RRAS may be contributing to these phenotypes. Critically, this study suggests that increased but physiological levels of the natural glucocorticoid can programme similar changes to those seen with pharmacological doses of the synthetic glucocorticoid. This may have important implications for women experiencing significant stress during pregnancy.

Effects of maternally administered drugs on the fetal and neonatal kidney

The number of pregnant women and women of childbearing age who are receiving drugs is increasing. A variety of drugs are prescribed for either complications of pregnancy or maternal diseases that existed prior to the pregnancy. Such drugs cross the placental barrier, enter the fetal circulation and potentially alter fetal development, particularly the development of the kidneys. Increased incidences of intrauterine growth retardation and adverse renal effects have been reported. The fetus and the newborn infant may thus experience renal failure, varying from transient oligohydramnios to severe neonatal renal insufficiency leading to death. Such adverse effects may particularly occur when fetuses are exposed to NSAIDs, ACE inhibitors and specific angiotensin II receptor type 1 antagonists. In addition to functional adverse effects, in utero exposure to drugs may affect renal structure itself and produce renal congenital abnormalities, including cystic dysplasia, tubular dysgenesis, ischaemic damage and a reduced nephron number. Experimental studies raise the question of potential long-term adverse effects, including renal dysfunction and arterial hypertension in adulthood. Although neonatal data for many drugs are reassuring, such findings stress the importance of long-term follow-up of infants exposed in utero to certain drugs that have been administered to the mother.

Maternal glucocorticoids and prenatal programming of hypertension

Maternal glucocorticoids have been postulated to play an important role in prenatal programming for adult hypertension in the offspring. However, we have shown previously that offspring hypertension caused by maternal dexamethasone subcutaneous administration at 100 microg x kg(-1) x day(-1) can be accounted for by the corresponding reduction in food intake that these mothers experience. The present studies were designed to determine whether there is a lower dose of dexamethasone that does not reduce maternal food intake yet still causes hypertension in the adult offspring. Pregnant rats were treated with subcutaneous dexamethasone at 50 (D50) or 25 (D25) microg x kg(-1) x day(-1) on days 15-20 of pregnancy. An additional group was untreated or received vehicle injections (control). D25 and D50 dams reduced their food intake by 17% during and after treatment and gained 31% less weight than control over the course of gestation. In adulthood ( approximately 21 wk), chronically instrumented male offspring of D50 and D25 had normal blood pressures (D50: 131 +/- 2 mmHg and D25: 127 +/- 3 mmHg vs. 127 +/- 2 mmHg in control). Qualitatively similar results were found in female offspring. Thus neither dexamethasone per se at these doses nor the accompanying modest reductions in maternal food intake and weight gain have blood pressure programming effects. As far as has been tested, there does not appear to be a dose of dexamethasone that, given over this time period in the rat, programs offspring hypertension without reducing maternal food intake and weight gain. These data do not support the hypothesis that maternal glucocorticoids program offspring hypertension directly.

Fetal programming of hypertension

Numerous epidemiological studies suggest an inverse relationship between low birth weight (LBW) and hypertension, an observation now supported by numerous animal studies. The mechanisms linking LBW and hypertension appear to be multifactorial and involve alterations in the normal regulatory systems and renal functions involved in the long-term control of arterial pressure. Recent studies using animal models of fetal programming suggest that programming during fetal life occurs in response to an adverse fetal environment and results in permanent adaptive responses that lead to structural and physiological alterations and the subsequent development of hypertension. This review summarizes the adaptive responses observed in the different models used to induce a suboptimal fetal environment and discusses insights into the mechanisms mediating the fetal programming of hypertension.

Modest maternal protein restriction fails to program adult hypertension in female rats

Modest maternal dietary protein restriction in the rat leads to hypertension in adult male offspring. The purpose of this study was to determine whether female rats are resistant to developing the increased blood pressure seen in male rats after maternal protein restriction. Pregnant rats were fed a normal protein (19%, NP) or low-protein (8.5%, LP) diet throughout gestation. Renal renin protein and ANG II levels were reduced by 50-65% in male LP compared with NP pups, but were not suppressed in female LP compared with female NP. Mean arterial pressure in conscious, chronically instrumented adult female offspring (22 wk) was not different in LP (LP: 120 +/- 3 mmHg vs. NP: 121 +/- 2 mmHg), and glomerular filtration rate was also not different in LP vs. NP. The number of glomeruli per kidney was similar in adult LP and NP female offspring (LP: 26,050 +/- 2,071 vs. NP: 26,248 +/- 1,292, NP), and individual glomerular volume was also not different (LP: 0.92 +/- 0.11 10(6) microm(3), LP vs. NP: 1.07 +/- 0.11 10(6) microm(3)); the total volume of all glomeruli per kidney was also not significantly different. Thus female rats are relatively resistant to the programming for adult hypertension by perinatal protein restriction that we have described in males. This resistance may be due to the fact that modest maternal protein restriction does not reduce the number of glomeruli with which females are endowed as it does in males. The intrarenal renin-angiotensin system during development may play a key role in this protective effect of female gender.