Defining the susceptible period of developmental toxicity for the AT1-selective angiotensin II receptor antagonist losartan in rats

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.

Intraperitoneal Administration of Telmisartan Prevents Postsurgical Adhesion Band Formation

BACKGROUND

Angiotensin II receptor blockers (ARBs) have a potential role in reducing inflammation and fibrosis. We have integrated systems and molecular biology approaches to investigate the therapeutic potential of ARBs in preventing postsurgical adhesion band formation.

MATERIAL AND METHODS

we have followed the ARRIVE guidelines point by point during experimental studies. Telmisartan (1 and 9 mg/kg), valsartan (1 and 9 mg/kg), and losartan (1 and 10 mg/kg) were administered intraperitoneally in different groups of male albino Wistar rat. After 7 d of treatment, macroscopic evidence and score of fibrotic bands based on scaling methods was performed. Moreover, the anti-inflammatory and antifibrosis effects of telmisartan on reduction of fibrotic bands were investigated by using histopathology, ELISA, and real-time polymerase chain reaction methods.

RESULTS

Telmisartan, but not losartan or valsartan, prevented the frequency as well as the stability of adhesion bands. Telmisartan appears to elicit anti-inflammatory responses by attenuating submucosal edema, suppressing proinflammatory cytokines, decreasing proinflammatory cell infiltration, and inhibiting oxidative stress at the site of peritoneal surgery. We also showed that telmisartan prevents fibrotic adhesion band formation by reducing excessive collagen deposition and suppression of profibrotic genes expression at the peritoneum adhesion tissues.

CONCLUSIONS

These results support the potential application of telmisartan in preventing postsurgical adhesion band formation by inhibiting key pathologic responses of inflammation and fibrosis in postsurgery patients.

Developmental milestones in neonatal and juvenile C57Bl/6 mouse - Indications for the design of juvenile toxicity studies

There is a growing demand for wild type mice and mouse models of disease that may be more representative of human conditions but there is little information on neonatal and juvenile mouse anatomy. This project produces sound and comprehensive histology background data on the developing neonatal mouse at different time points from Day 0 until Day 28. The work describes optimal methods for tissue harvesting, fixation and processing from the neonatal and juvenile mice which can be used in routine toxicology studies. A review of the available literature revealed inconsistencies in the developmental milestones reported in the mouse. Although it is true that the sequence of events during the development is virtually the same in mice and rats, important developmental milestones in the mouse often happen earlier than in the rat, and these species should not be used interchangeably.

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.

Scientific and Regulatory Policy Committee Points to Consider Review: Inclusion of Reproductive and Pathology End Points for Assessment of Reproductive and Developmental Toxicity in Pharmaceutical Drug Development

Standard components of nonclinical toxicity testing for novel pharmaceuticals include clinical and anatomic pathology, as well as separate evaluation of effects on reproduction and development to inform clinical development and labeling. General study designs in regulatory guidances do not specifically mandate use of pathology or reproductive end points across all study types; thus, inclusion and use of these end points are variable. The Scientific and Regulatory Policy Committee of the Society of Toxicologic Pathology (STP) formed a Working Group to assess the current guidelines and practices on the use of reproductive, anatomic pathology, and clinical pathology end points in general, reproductive, and developmental toxicology studies. The Working Group constructed a survey sent to pathologists and reproductive toxicologists, and responses from participating organizations were collected through the STP for evaluation by the Working Group. The regulatory context, relevant survey results, and collective experience of the Working Group are discussed and provide the basis of each assessment by study type. Overall, the current practice of including specific end points on a case-by-case basis is considered appropriate. Points to consider are summarized for inclusion of reproductive end points in general toxicity studies and for the informed use of pathology end points in reproductive and developmental toxicity studies.

Placental transfer and mammary excretion of a novel angiotensin receptor blocker fimasartan in rats

Background

Fimasartan (FMS) is a potent angiotensin receptor blocker for the treatment of mild to moderate hypertension. This study aimed to evaluate the transfer of FMS to fetus and breast milk in rats.

Methods

In order to study the transfer to the fetus and nursing pup, pregnant and nursing maternal rats were administered with FMS by a constant intravenous infusion to reach target plasma concentrations of 200 ng/mL and 100 ng/mL. The concentrations of FMS in plasma, placenta, amniotic fluid, fetus, and milk were determined by a validated LC-MS/MS assay.

Results

Upon constant intravenous infusion, the plasma FMS concentration reached the target steady state concentrations (C_ss = 200 ng/mL and 100 ng/mL) in 24 h. The tissue-to-plasma partition coefficients (K_p) for placenta, amniotic fluid, and milk were obtained based on the observed FMS concentrations in the tissues and C_ss. The K_p values for all tissues were not different between high (C_ss = 200 ng/mL) and low (C_ss = 100 ng/mL) dose groups. While the mean K_p of the placenta was 44.6–59.0 %, the mean K_p was 1.3–1.7 % for the amniotic fluid and 14.9–17.0 % for fetus. The mean K_p of milk was 10.4–15.2 %.

Conclusions

Placental transfer and milk excretion of FMS was relatively lower compared to other angiotensin receptor blockers.

Characterization of Hydronephrosis in Neonatal Rats from Dams Receiving Candesartan Cilexetil (TCV-116), an Angiotensin II Type 1 Receptor Antagonist

The characteristics and mechanisms of hydronephrosis in neonatal rats induced by candesartan cilexetil (TCV-116), a potent angiotensin II (AngII) type 1 receptor antagonist, were examined. TCV-116 (300 mg/kg/day) was orally administered to dams for 4 weeks from gestation day 15 through lactation day 21. On lactation days 0, 4, 7, 14, and 22, the kidneys of the pups were examined. Hydronephrosis was observed starting on lactation day 14 accompanied by other histological changes, atrophy of the renal papillary tubules, dilatation of the renal tubules, and basophilic renal tubules in the cortex. These changes could also be observed at 10 weeks of age, 7 weeks after the last dose was administered. These renal structural abnormalities were consistent with that seen in other renin-angiotensin system antagonists. TCV-116 (300 mg/kg/day) was then administered to dams for four separate 1-week periods: gestation days 15 through 21, lactation days 0 to 6, lactation days 7 to 13, and lactation days 14 to 21. Pups were most susceptible to the induction of hydronephrosis when TCV-116 was administered from lactation days 0 to 6 and lactation days 7 to 13. The increased incidence of hydronephrosis and renal histological changes in the pups was prevented by administering mineralocorticoid, deoxycorticosterone acetate (10 mg/kg/day), subcutaneously to the pups from lactation days 7 to 13. Also, plasma aldosterone concentration in the pups was decreased after three daily treatments of TCV-116, accompanied by the increased plasma potassium concentration and urine Na/K ratio and the decreased urine osmolality. Therefore, we considered that the development of hydronephrosis in pups is closely related to the AngII blockade for the first 2 weeks after birth, and the reduction of aldosterone secretion by the inhibition of AngII leads to the disorder of the sodium and potassium homeostasis in neonates, and subsequent increase in urine volume may be involved in the mechanisms of hydronephrosis. We conclude that the hydronephrosis was caused by the sodium imbalance resulted from the pharmacological action of TCV-116 during the neonatal period.

Tenofovir during pregnancy in rats: a novel pathway for programmed hypertension in the offspring

OBJECTIVES

To evaluate the occurrence of systemic and renal abnormalities in the offspring of Wistar rats exposed to tenofovir disoproxil fumarate (DF) during pregnancy.

METHODS

Female Wistar rats received a standard diet, with or without addition of tenofovir DF (100 mg/kg diet), 1 week before mating and during pregnancy. Offspring from the tenofovir DF group were placed with an untreated foster mother during breastfeeding and compared with offspring from rats maintained on a standard diet during mating and pregnancy (control). Control and tenofovir DF were followed up at 3 and 6 months of age. Monthly body weight and systolic blood pressure (SBP), glomerular counts, renal function, biochemical parameters, angiotensin II, renal renin angiotensin aldosterone system (RAAS) and renal sodium transporters were analysed.

RESULTS

Tenofovir DF offspring showed lower birth weight compared with the control group. After the third month, growth among the tenofovir DF group experienced a rapid catch-up. SBP increased progressively after the second month of age in the tenofovir DF group. Nephron number did not differ between the groups; however, the tenofovir DF group showed glomerular structural changes. Plasma aldosterone was higher in the tenofovir DF group, associated with a significant increase in renal expression of RAAS. The tenofovir DF rats showed up-regulation of renal sodium transporters and consequently lower urinary sodium excretion.

CONCLUSIONS

This is the first demonstration using an experimental model that maternal exposure to tenofovir DF during gestation results in overactivation of RAAS, up-regulation of renal sodium transporters and hypertension in the offspring.

The role of oxidative stress in renal injury induced in rats by losartan exposure during lactation

INTRODUCTION

Rats exposed to angiotensin II (AII) receptor antagonists during lactation present progressive disturbances in renal development that lead to progressive alterations in renal function and structure. This study evaluates the role of oxidative stress in the renal changes induced by exposure to losartan, a type 1 AII receptor antagonist, in rats during lactation.

MATERIALS AND METHODS

Male Wistar pups were divided into: Control, pups of dams that received 2% sucrose solution; Control-tempol, pups of dams that received tempol (0.34 g/l), a superoxide dismutase mimetic compound; Losartan, pups of dams that received losartan (100 mg/kg/day), and Losartan-tempol, pups of dams that received losartan and tempol. Losartan and/or tempol were administered during lactation. Blood and urine samples were collected at 21 or 60 days, and the kidneys were removed.

RESULTS

Losartan-treated pups exhibited disturbances in renal function and structure that persisted into adulthood. Tempol treatment reduced oxidative stress and attenuated the changes induced by losartan in the glomerular filtration rate, desmin expression at the glomerular edge, vimentin in tubular cells, as well as apoptosis and inflammatory infiltration in the renal cortex.

CONCLUSION

Oxidative stress contributes at least in part to the renal injury observed in pups exposed to losartan during lactation.

Is there an embryopathy associated with first-trimester exposure to angiotensin-converting enzyme inhibitors and angiotensin receptor antagonists? A critical review of the evidence

Drugs that interfere with the renin-angiotensin system, such as angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs), are widely used to manage hypertension and heart failure. Adequate functioning of the RAS is essential for normal fetal kidney development. The potential for ACEIs and ARBs to impair fetal and neonatal renal function if taken after the first trimester of pregnancy has been well documented. Although these drugs were not found to be teratogenic in animals, until recently little was known about the teratogenic effects of ACEIs and ARBs in humans when exposure was limited to the first trimester of pregnancy. New evidence from epidemiologic studies indicates that there may be an elevated teratogenic risk when these drugs are taken during the first trimester of pregnancy. However, this elevated risk does not appear to be specific to ACEIs and ARBs, but is instead related to maternal factors and diseases that typically coexist with hypertension in pregnancy, such as diabetes, advanced maternal age, and obesity. Women who become pregnant while being treated with an ACEI or ARB should be advised to avoid exposure to these drugs during the second and third trimesters of pregnancy by switching to a different class of antihypertensive drugs between weeks 8 and 10 after conception.

Angiotensin converting enzyme inhibition blocks interstitial hyaluronan dissipation in the neonatal rat kidney via hyaluronan synthase 2 and hyaluronidase 1

A functional renin-angiotensin system (RAS) is required for normal kidney development. Neonatal inhibition of the RAS in rats results in long-term pathological renal phenotype and causes hyaluronan (HA), which is involved in morphogenesis and inflammation, to accumulate. To elucidate the mechanisms, intrarenal HA content was followed during neonatal completion of nephrogenesis with or without angiotensin converting enzyme inhibition (ACEI) together with mRNA expression of hyaluronan synthases (HAS), hyaluronidases (Hyal), urinary hyaluronidase activity and cortical lymphatic vessels, which facilitate the drainage of HA from the tissue. In 6-8days old control rats cortical HA content was high and reduced by 93% on days 10-21, reaching adult low levels. Medullary HA content was high on days 6-8 and then reduced by 85% to 12-fold above cortical levels at day 21. In neonatally ACEI-treated rats the reduction in HA was abolished. Temporal expression of HAS2 corresponded with the reduction in HA content in the normal kidney. In ACEI-treated animals cortical HAS2 remained twice the expression of controls. Medullary Hyal1 increased in controls but decreased in ACEI-treated animals. Urine hyaluronidase activity decreased with time in control animals while in ACEI-treated animals it was initially 50% lower and did not change over time. Cells expressing the lymphatic endothelial mucoprotein podoplanin in ACEI-treated animals were increased 18-fold compared to controls suggesting compensation. In conclusion, the high renal HA content is rapidly reduced due to reduced HAS2 and increased Hyal1 mRNA expressions. Normal angiotensin II function is crucial for inducing these changes. Due to the extreme water-attracting and pro-inflammatory properties of HA, accumulation in the neonatally ACEI-treated kidneys may partly explain the pathological renal phenotype of the adult kidney, which include reduced urinary concentration ability and tubulointerstitial inflammation.

The detrimental role of angiotensin receptor agonistic autoantibodies in intrauterine growth restriction seen in preeclampsia

Growth-restricted fetuses are at risk for a variety of lifelong medical conditions. Preeclampsia, a life-threatening hypertensive disorder of pregnancy, is associated with fetuses who suffer from intrauterine growth restriction (IUGR). Recently, emerging evidence indicates that preeclamptic women harbor AT₁ receptor agonistic autoantibodies (AT₁-AAs) that contribute to the disease features. However, the exact role of AT₁-AAs in IUGR and the underlying mechanisms have not been identified. We report that these autoantibodies are present in the cord blood of women with preeclampsia and retain the ability to activate AT₁ receptors. Using an autoantibody-induced animal model of preeclampsia, we show that AT₁-AAs cross the mouse placenta, enter fetal circulation, and lead to small fetuses with organ growth retardation. AT₁-AAs also induce apoptosis in the placentas of pregnant mice, human villous explants, and human trophoblast cells. Finally, autoantibody-induced IUGR and placental apoptosis are diminished by either losartan or an autoantibody-neutralizing peptide. Thus, these studies identify AT₁-AA as a novel causative factor of preeclampsia-associated IUGR and offer two possible underlying mechanisms: a direct detrimental effect on fetal development by crossing the placenta and entering fetal circulation, and indirectly through AT₁-AA–induced placental damage. Our findings highlight AT₁-AAs as important therapeutic targets.

Fetal and neonatal consequences of antenatal exposure to type 1 angiotensin II receptor-antagonists

Sartans are selective type 1 angiotensin II receptor-antagonists that are used in the treatment of arterial hypertension. Few reports are available concerning the use of sartans during pregnancy. We report two cases of adverse fetal outcome in hypertensive pregnancies exposed to sartans. In the first case, anamnios and fetal renal failure due to severe tubular dysgenesia led to termination of pregnancy in the 27th week. The second patient presented with hypocalvaria and developed fetal renal failure. The use of sartans during the two last trimesters of pregnancy should be strictly avoided.

MAPK and angiotensin II receptor in kidney of newborn rats from losartan-treated dams

Several lines of evidence suggest that angiotensin II (A-II) participates in the postnatal development of the kidney in rats. Many effects of A-II are mediated by mitogen-activated protein kinase (MAPK) pathways. This study investigated the influence that treatment with losartan during lactation has on MAPKs and on A-II receptor types 1 (AT(1)) and 2 (AT(2)) expression in the renal cortices of the offspring of dams exposed to losartan during lactation. In addition, we evaluated the relationship between such expression and changes in renal function and structure. Rat pups from dams receiving 2% sucrose or losartan diluted in 2% sucrose (40 mg/dl) during lactation were killed 30 days after birth, and the kidneys were removed for histological, immunohistochemical, and Western blot analysis. AT(1) and AT(2) receptors and p-p38, c-Jun N-terminal kinases (p-JNK) and extracellular signal-regulated protein kinases (p-ERK) expression were evaluated using Western blot analysis. The study-group rats presented an increase in AT(2) receptor and MAPK expression. In addition, these rats also presented lower glomerular filtration rate (GFR), greater albuminuria, and changes in renal structure. In conclusion, newborn rats from dams exposed to losartan during lactation presented changes in renal structure and function, which were associated with AT(2) receptor and MAPK expression in the kidneys.

Reversible acute fetal renal failure due to maternal exposure to angiotensin receptor blocker

We report on a case of fetal toxicity due to maternal treatment with olmesartan medoxomil. At 29 weeks' gestation, oligohydramnios was found, although the fetus had normal kidneys on ultrasound evaluation. Withdrawal of olmesartan medoxomil, maternal rehydration, and a single dose of furosemide reversed the renal impairment. After term delivery, the neonate was confirmed to have normal renal function. The case suggested that fetal renal impairment due to olmesartan medoxomil may be reversible.

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.

Consequences of Intrauterine Growth Restriction for the Kidney

Low birth weight due to intrauterine growth restriction is associated with various diseases in adulthood, such as hypertension, cardiovascular disease, insulin resistance and end-stage renal disease. The purpose of this review is to describe the effects of intrauterine growth restriction on the kidney. Nephrogenesis requires a fine balance of many factors that can be disturbed by intrauterine growth restriction, leading to a low nephron endowment. The compensatory hyperfiltration in the remaining nephrons results in glomerular and systemic hypertension. Hyperfiltration is attributed to several factors, including the renin-angiotensin system (RAS), insulin-like growth factor (IGF-I) and nitric oxide. Data from human and animal studies are presented, and suggest a faltering IGF-I and an inhibited RAS in intrauterine growth restriction. Hyperfiltration makes the kidney more vulnerable during additional kidney disease, and is associated with glomerular damage and kidney failure in the long run. Animal studies have provided a possible therapy with blockage of the RAS at an early stage in order to prevent the compensatory glomerular hyperfiltration, but this is far from being applicable to humans. Research is needed to further unravel the effect of intrauterine growth restriction on the kidney.

Further insights into the role of angiotensin II in kidney development

Over the past decade, compelling studies have highlighted the fundamental role of the renin-angiotensin system (RAS) in renal development and long-term control of renal function and arterial pressure. The present review provides an update of the understanding of how the RAS controls nephrogenesis and nephrovascular development. In addition, the investigations linking the perinatal development of RAS inhibition-induced renal dysmorphology and establishment of adult blood pressure are discussed.

Foetal kidney maldevelopment in maternal use of angiotensin II type I receptor antagonists

We report renal lesions observed in a foetus exposed throughout pregnancy to angiotensin II type I (AT 1) receptor antagonists. The mother suffered from essential hypertension and was treated with Cozaar (losartan 50 mg). Autopsy examination of the foetus revealed severe renal lesions, including tubular dysgenesis, hypertrophy of the endothelial and medial cells lining the arterial and arteriolar walls, hyperplasia of the juxtaglomerular apparatus and poorly developed vasa recta. Similar lesions have already been observed in foetuses of women treated with angiotensin-converting enzyme antagonists and also in foetuses and neonates of animals undergoing experimental blockade of the renin-angiotensin system. The purpose of this report is to describe structural lesions observed in the kidneys, and, particularly, vascular lesions. Our results suggest that the use of AT 1 receptor antagonists during pregnancy may have a severe deleterious effect on kidney development in the foetus.

Tubular mitochondrial alterations in neonatal rats subjected to RAS inhibition

Pharmacological interruption of the angiotensin II (ANG II) type 1 receptor signaling during nephrogenesis in rats perturbs renal tubular development. This study aimed to further investigate tubular developmental defects in neonatal rats subjected to ANG II inhibition with enalapril. We evaluated tubular ultrastructural changes using electron microscopy and estimated spectrophotometrically activity or concentrations of succinate dehydrogenase (SDH), cytochromes a and c, which are components of mitochondrial respiratory chain, on postnatal days 2 and 9 (PD2 and PD9). Renal expression of sodium-potassium adenosinetriphosphatase (Na+-K+-ATPase) and two reflectors of mitochondrial biogenesis [mitochondrial transcription factor A (TFAM) and translocase of outer mitochondrial membrane 20 (TOM20)] also were studied using Western immunoblotting and immunohistochemistry. Enalapril disrupted inner mitochondrial membranes of developing cortical and medullary tubular cells on PD2 and PD9. These findings were paralleled by impaired mitochondrial respiratory function, as revealed from the changes in components of the mitochondrial respiratory chain, such as decreased cytochrome c level in the cortex and medulla on PD2 and PD9, decreased cytochrome a level in the cortex and medulla on PD2, and diminished cortical SDH activity on PD2 and PD9. Moreover, tubular expression of the most active energy-consuming pump Na+-K+-ATPase was decreased by enalapril treatment. Renal expression of TFAM and TOM20 was not altered by neonatal enalapril treatment. Because nephrogenesis is a highly energy-demanding biological process, with the energy being utilized for renal growth and transport activities, the structural-functional alterations of the mitochondria induced by neonatal enalapril treatment may provide the propensity for the tubular developmental defect.

Losartan, an AT1 antagonist, prevents aortic aneurysm in a mouse model of Marfan syndrome

Aortic aneurysm and dissection are manifestations of Marfan syndrome (MFS), a disorder caused by mutations in the gene that encodes fibrillin-1. Selected manifestations of MFS reflect excessive signaling by the transforming growth factor-beta (TGF-beta) family of cytokines. We show that aortic aneurysm in a mouse model of MFS is associated with increased TGF-beta signaling and can be prevented by TGF-beta antagonists such as TGF-beta-neutralizing antibody or the angiotensin II type 1 receptor (AT1) blocker, losartan. AT1 antagonism also partially reversed noncardiovascular manifestations of MFS, including impaired alveolar septation. These data suggest that losartan, a drug already in clinical use for hypertension, merits investigation as a therapeutic strategy for patients with MFS and has the potential to prevent the major life-threatening manifestation of this disorder.

Clinical pharmacokinetics of losartan

Losartan is the first orally available angiotensin-receptor antagonist without agonist properties. Following oral administration, losartan is rapidly absorbed, reaching maximum concentrations 1-2 hours post-administration. After oral administration approximately 14% of a losartan dose is converted to the pharmacologically active E 3174 metabolite. E 3174 is 10- to 40-fold more potent than its parent compound and its estimated terminal half-life ranges from 6 to 9 hours. The pharmacokinetics of losartan and E 3174 are linear, dose-proportional and do not substantially change with repetitive administration. The recommended dosage of losartan 50 mg/day can be administered without regard to food. There are no clinically significant effects of age, sex or race on the pharmacokinetics of losartan, and no dosage adjustment is necessary in patients with mild hepatic impairment or various degrees of renal insufficiency. Losartan, or its E 3174 metabolite, is not removed during haemodialysis. The major metabolic pathway for losartan is by the cytochrome P450 (CYP) 3A4, 2C9 and 2C10 isoenzymes. Overall, losartan has a favorable drug-drug interaction profile, as evidenced by the lack of clinically relevant interactions between this drug and a range of inhibitors and stimulators of the CYP450 system. Losartan does not have a drug-drug interaction with hydrochlorothiazide, warfarin or digoxin. Losartan should be avoided in pregnancy, as is the case with all other angiotensin-receptor antagonists. When given in the second and third trimester of pregnancy, losartan is often associated with serious fetal toxicity. Losartan is a competitive antagonist that causes a parallel rightward shift of the concentration-contractile response curve to angiotensin-II, while E 3174 is a noncompetitive "insurmountable" antagonist of angiotensin-II. The maximum recommended daily dose of losartan is 100mg, which can be given as a once-daily dose or by splitting the same total daily dose into two doses. Losartan reduces blood pressure comparably to other angiotensin-receptor antagonists. Losartan has been extensively studied relative to end-organ protection, with studies having been conducted in diabetic nephropathy, heart failure, post-myocardial infarction and hypertensive patients with left ventricular hypertrophy. The results of these studies have been sufficiently positive to support a more widespread use of angiotensin-receptor antagonists in the setting of various end-organ diseases. Losartan, like other angiotensin-receptor antagonists, is devoid of significant adverse effects.

Histopathological and ultrastructural effects of Losartan on embryonic rat kidney

The aim of our study was to investigate the histopathological, immunohistochemical and ultrastructural effects of Losartan (a selective angiotensin II type-1 receptor blocker) on renal development in rats. Twelve pregnant rats were divided into control and experimental groups. In the experimental group, Losartan (10 mg/kg/day) was given via nasogastric tube, between the sixth day of implantation and time of sacrifice on embryonic days 18 and 20. All formalin-fixed, paraffin wax-embedded renal tissue sections were stained with hematoxylin and eosin or labelled for binding of primary antibodies against transforming growth factor-beta (TGF-beta 1,-2,-3) using an avidin-biotin-peroxidase method. For electron microscopic examination, samples were fixed with glutaraldehyde and osmium tetroxide and embedded in araldite. Glomerular basement membrane (GBM) thickness was measured and compared using an unpaired t-test. Angiotensin II type-1 receptor antagonism by Losartan inhibited renal growth and delayed nephron maturation. Increased immunoreactivity of TGF-beta's was observed in developing nephron precursors and interstitial cells in the experimental group. Electron microscopical examination showed that thickening of the GBM was normal in the control group but an irregular thickening was seen in the experimental group (p < 0.001). It was also seen that epithelial cells of developing tubules underwent apoptosis in the experimental group. Thus, renal development in rats seems to depend on an intact renin-angiotensin system.

Losartan in cardiovascular disease

Hypertension is a major risk factor for the development of cardiovascular disease. Numerous placebo-controlled trials have demonstrated that treatment of hypertension results in substantial reduction of hypertension-related vascular events. The benefit of specific therapies beyond their effect on blood pressure is well established. Losartan is an orally-active, selective, nonpeptide, angiotensin II type 1-receptor antagonist (ARB), and it was the first in this class to be marketed. Several large-scale clinical trials have demonstrated that losartan and other ARBs have benefits in preventing cardiovascular disease. The Losartan Intervention For End point reduction in hypertension (LIFE) study demonstrated improved outcomes with losartan as compared with atenolol-based therapies in hypertensive patients with left ventricular hypertrophy, mainly because of stroke prevention. The Reduction of End points in Non-insulin-dependent diabetes mellitus with the Angiotensin II Antagonist Losartan (RENAAL) study demonstrated that losartan prevented the progression of diabetic nephropathy. In this review, evidence from these and other clinical trials with losartan shall be discussed. The pharmacodynamic and pharmacokinetic properties of losartan are described to explain its mechanisms of action. Among the ARB class, losartan possesses certain unique properties, which may enhance its cardiovascular protective effects. These include an increase of urinary uric acid excretion and antiatherothrombotic properties. Potential future roles for losartan and other ARBs shall be discussed, in addition to emphasizing areas in which evidence is currently lacking or indecisive, including head-to-head comparisons of ARBs and the effects of combining an ARB with angiotensin-converting-enzyme inhibitors.

Effects of drugs on the fetus

Most drugs are not labelled for use in pregnancy. Consequently, large numbers of women expose their fetus to potential risks, either because they do not know that they are pregnant or because they require treatment for gestational pathologies. The present review focuses on drug classes for which the risk:benefit ratio during pregnancy has been discussed recently based on human data. Selective serotonin reuptake inhibitors have gained wide acceptance in the treatment of depression and data on their risk for neonatal adaptation after late exposure are reviewed. Angiotensin converting enzyme inhibitors and angiotensin II receptors antagonists interact with the renin-angiotensin system, although with different mechanisms, and might cause severe fetal tubular dysgenesis. Non-steroidal anti-inflammatory and antiviral drugs and recreational drugs are also presented.

Angiotensin II receptor antagonist treatment during pregnancy

Angiotensin II (A-II) is the main effector of the renin-angiotensin system. A-II functions by binding its type 1 (AT1) receptors to cause vasoconstriction and retention of sodium and fluid. Several AT1 receptor antagonists-a group of drugs collectively called "sartans"-have been marketed during the past few years for treatment of hypertension and heart failure. At least 15 case reports describe oligohydramnios, fetal growth retardation, pulmonary hypoplasia, limb contractures, and calvarial hypoplasia in various combinations in association with maternal losartan, candesartan, valsartan, or telmisartan treatment during the second or third trimester of pregnancy. Stillbirth or neonatal death is frequent in these reports, and surviving infants may exhibit renal damage. The fetal abnormalities, which are strikingly similar to those produced by maternal treatment with angiotensin-converting enzyme (ACE) inhibitors during the second and third trimesters of pregnancy, are probably related to extreme sensitivity of the fetus to the hypotensive action of these drugs. Very little information is available regarding the outcome of human pregnancies in which the mother was treated with an AT1 receptor antagonist during the first trimester, but animal studies have not demonstrated teratogenic effects after maternal treatment with large doses of AT1 receptor antagonists during organogenesis. We conclude that pharmacological suppression of the fetal renin-angiotensin system through ACE inhibition or AT1 receptor blockade seems to disrupt fetal vascular perfusion and renal function. We recommend that maternal treatment with AT1 receptor antagonists be avoided during the second and third trimesters of pregnancy and that women who become pregnant while taking one of these medications be changed to an antihypertensive drug of a different class as soon as the pregnancy is recognized.

Fetal Toxic Effects of Angiotensin II Receptor Antagonists: Case Report and Follow-Up after Birth

OBJECTIVE:

To report a child born with renal impairment following severe anhydramnios due to maternal exposure to an angiotensin II receptor type 1 (AT1) antagonist, valsartan, and hydrochlorothiazide during the first 28 weeks of pregnancy.

CASE SUMMARY:

A hypertensive woman treated with valsartan 80 mg/day, hydrochlorothiazide 12.5 mg/day, prazosin 10 mg/day, lysine acetylsalicylate 100 mg/day, and levothyroxine 250 μg/day became pregnant. At 28 weeks' gestational age, severe anhydramnios associated with high β2-microglobulin levels in the fetal blood cord was observed. Upon discontinuation of valsartan, fetal renal prognosis improved. In this case, using the Naranjo probability scale, the renal insufficiency of the child was probably related to valsartan. At the age of 2.5 years, the child presented with only mild chronic renal insufficiency. Growth parameters were within the normal range, and there was no evidence of developmental delay.

DISCUSSION:

Exposure to AT1 antagonists during the second part of pregnancy can lead to abnormalities similar to those observed after exposure to angiotensin-converting enzyme inhibitors, that is, reduced fetal kidney perfusion that may result in oligoamnios and neonatal renal insufficiency. Fourteen previous reports of maternal exposure to AT1 antagonists during this period have been published. In 6 cases, fetal or neonatal death occurred; in 2 cases, pregnancy was terminated because of complete anhydramnios or fetal abnormalities; in 1 case, renal insufficiency persisted at 8 months of age; in 2 cases, kidney function was fairly normal at birth; and in 4 cases, including the one described here, neonatal renal failure improved in the first year of life.

CONCLUSIONS:

AT1 antagonists should be avoided throughout pregnancy. If these agents are prescribed accidentally to a pregnant woman, monitoring of amniotic fluid volume and β2-microglobulin fetal blood levels after discontinuation of the AT1 antagonist can provide critical data for advising parents on pregnancy and fetal outcome.

AT1 and AT2 receptor in the kidney: role in health and disease

The renin angiotensin system plays an important role in the control of body fluid and electrolyte homeostasis and blood pressure regulation. Angiotensin II is the most effector hormone of this system and functions mainly through stimulation of its subtype receptors, namely, the AT1 and AT2 receptors. Most of the known physiological and pathologic effects of angiotensin II are mediated through stimulation of the AT1 receptor. The knowledge about the involvement of the AT2 receptor in physiological and pathologic processes is still evolving. In the kidney, both the AT1 and AT2 receptors contribute to the regulation of renal hemodynamic and tubular functions. Also, these receptors regulate renal cellular growth and matrix formation. However, AT2 receptor possesses functions that counteract the effects of the AT1 receptor. The balance between the AT1 and AT2 receptors can determine the renal status in health and disease.

An essential role for angiotensin II type 1a receptor in pregnancy-associated hypertension with intrauterine growth retardation

Little is known about an in vivo significance of angiotensin II Type-1 receptor (AT1) for pregnancy-associated diseases, including hypertension and intrauterine growth retardation (IUGR). We previously demonstrated that female mice carrying the human angiotensinogen gene (hAG+/+), when mated with human renin transgenic (hRN+/+) male mice, displayed hypertension in late pregnancy due to secretion of human renin from the fetal side into the maternal circulation. In the present study, to investigate a role for AT1 in pregnancy-associated hypertension, we generated a new strain of hAG+/+/mAT1a-/- mice by genetically deleting the AT1a gene from hAG+/+ mice. When mated with hRN+/+ male mice, excessive increases in human renin, angiotensin, and plasma renin activity were detected in the plasma of pregnant hAG+/+/mAT1a-/- mice as found in that of pregnant hAG+/+ mice. Surprisingly, however, blood pressure of hAG+/+/mAT1a-/- mice was not elevated in late pregnancy despite the presence of AT1b, a subtype of AT1. The maternal and fetal defects, such as cardiac and placental abnormalities, and IUGR observed in pregnant hypertensive hAG+/+ mice were not recognized in pregnant hAG+/+/mAT1a-/- mice. The limited term administration of AT1 antagonists to hypertensive hAG+/+ mice in late pregnancy dramatically improved hypertension and IUGR, showing the clinical importance of AT1a.

Insulin and losartan reduce proteinuria and renal hypertrophy in the pregnant diabetic rat

This study was designed to investigate the effect of hyperglycemia and angiotensin II (AngII) on renal hypertrophy and proteinuria in the pregnant diabetic rat. Secondary objectives were to evaluate changes in components of the renin-angiotensin axis and the effects of administration of losartan on pregnancy outcome. Fifty-three pregnant rats were allocated to 6 groups (1) nondiabetic controls (n = 12), (2) nondiabetic controls administered losartan (70-80 mg/kg/day; n = 10), (3) rats in which intravenous streptozotocin (STZ) was used to induce diabetes (55 mg/kg on day 10 of pregnancy; n = 10), (4) diabetic rats treated with losartan (n = 7), (5) diabetic rats treated with insulin (4 U/day; n = 7), and (6) diabetic rats treated with insulin and losartan (n = 7). Urinary protein excretion measured 4 days after STZ was 4 times greater in the rats with STZ-induced diabetes and significantly less in diabetic rats given losartan, insulin, or both. Postpartum kidney weight was greater in the rats with STZ-induced diabetes (2.04 +/- 0.21 g) than in the controls (1.37 +/- 0.14 g; P <.05) and reduced in the diabetic rats given losartan, insulin, or both (1.57 +/- 0.22, 1.73 +/- 0.13, and 1.51 +/- 0.14 g, respectively; P <.05). Plasma levels of angiotensin II in rats given losartan were more than 3.5 times greater than those in controls (749 +/- 436, 596 +/- 323, 567 +/- 349, and 159 +/- 28 pg/mL; P <.001). Postpartum activity of angiotensin-converting enzyme was increased in the untreated diabetic rats compared with that in control rats (162 +/- 12 vs 117 +/- 16 nmol/mL/min; P <.05). This increase was abolished by treatment with losartan or insulin. The number of newborns and mean weight of each newborn was similar in all groups. In summary, administration of losartan or insulin prevented, in part, kidney hypertrophy and protein excretion in the diabetic pregnant rat. Losartan did not affect the number or weight of newborns. Because angiotensin II receptor-blockers are contraindicated in pregnancy, good control of diabetes through the use of insulin should be advantageous.

Neonatal acute renal failure secondary to maternal exposure to telmisartan, angiotensin II receptor antagonist

Fetal and neonatal toxic effects of angiotensin II receptor antagonists have been described in animals and humans. Five cases of fetal or neonatal deaths have been reported following maternal use of sartans for hypertension. We report a case of neonatal transient renal failure following telmisartan therapy during pregnancy. This class of antihypertensive drugs should be avoided during pregnancy and breastfeeding.

The renin angiotensin system and kidney development

When angiotensin II or AT1 receptor is experimentally inhibited during the perinatal period, either by pharmacological intervention or genetic manipulation, the kidney develops with profound structural abnormalities. Most prominent are hypertrophy of arterial vasculatures and atrophy of the papilla. Although the mechanism by which the vascular hypertrophy occurs remains unknown, study of the atrophic papilla gives us a new clue for understanding the physiological role of angiotensin. Mutant mice completely devoid of AT1 receptor fail to develop the renal pelvis and the ureteral peristaltic movement. Normally, angiotensin and AT1 receptor are transiently up-regulated around the renal outlet at birth. Thus angiotensin II induces the peristaltic machinery during the perinatal period in a timely fashion to accommodate the dramatic increase in urine production that occurs during the transition from intra- to extra-uterine life. Further studies revealed that in adult animals angiotensin augments the peristaltic movement when the urinary tract is partially obstructed, thereby protecting the kidney from hydronephrosis. This newly discovered function of angiotensin to protect kidney architecture at the time of urine outflow obstruction is reminiscent of its similar kidney structure-protecting function that is active during arterial blood flow obstruction.

AT(1) receptor blockade with losartan during gestation in Wistar rats leads to an increase in thirst and sodium appetite in their adult female offspring

We studied the effects of angiotensin II receptor blockade with losartan on thirst and sodium appetite in pregnant Wistar rats and on their adult female offspring. During maternal adaptation to pregnancy, average daily total water intake increased by 63% (P<0.01); NaCl intake by 214% (P<0.001). These changes were not blocked by daily s.c. injections of losartan (50 mg/kg bw i.p.) from gestation day (GD) 2 until GD 19 which implied that maternal AT(1) receptors were not involved in the up regulation of thirst and sodium appetite during pregnancy. Losartan blockade during gestation led to a significant and continued increase in thirst and sodium appetite in the adult female offspring. Daily water intakes were greater in the losartan (LO) group than in the vehicle-injected control group (CO), leading to a total water intake of 1114 +/- 80.6 ml/kg bw compared with 738 +/- 56.7 ml/kg bw (P<0.05) during the 8-day period of observation. Daily sodium intakes were usually 2-3 times greater in the LO group compared with the CO group, amounting to a final cumulative intake of 232 +/- 33 mmol/kg bw compared with 93.8 +/- 16.5 mmol/kg bw (P<0.05) in 8 days. These elevated sodium and water intakes were nearly counterbalanced by the increased renal excretion of water and sodium by fully functional kidneys that were not injured by the drug. Body weights were 10% lower in the LO group at the start but remained unchanged relative to the CO group during the entire 8-day period of observation. Plasma electrolytes, blood hematocrit and carotid MABP in the LO group did not differ from the CO group.

Losartan and fetal toxic effects

We report a case of maternal exposure to the antihypertensive drug losartan during weeks 20-31 of pregnancy. We saw the fetal toxic effects of oligohydramnios (decreased amniotic fluid), fetal pulmonary hypoplasia, fetal hypoplastic skull bones, and subsequent fetal death. This pattern of abnormalities is similar to those seen in exposure to angiotensin-converting-enzyme (ACE) inhibitors during pregnancy, and were probably caused by losartan.

IGF-I treatment attenuates renal abnormalities induced by neonatal ACE inhibition

An intact renin-angiotensin system (RAS) during nephrogenesis is essential for normal renal development. We have shown previously that neonatal inhibition of the RAS, either with ANG II type 1-receptor blockade or angiotensin-converting enzyme (ACE) inhibition, induces irreversible renal abnormalities. The aim of the present study was to investigate whether an interrupted RAS can be compensated for by exogenous administration of another important renal growth-promoting factor, the insulin-like growth factor-I (IGF-I). Rats were treated daily with either the ACE inhibitor enalapril (10 mg/kg), recombinant human IGF-I (3 mg/kg), or the combination enalapril + IGF-I from perinatal day 3 to 13. Urinary concentrating ability, renal function, and renal morphology were assessed at adult age. The gene expression and localization of IGF-I, its receptor, and the growth hormone receptor (GHR) were investigated during ongoing ACE inhibition. The present study demonstrates normalized renal function and histology in enalapril + IGF-I-treated animals. Ongoing ACE inhibition suppressed the medullary IGF-I mRNA expression and altered the local distribution of both IGF-I and GHR. Thus the present study provides evidence for an interaction between the RAS and GH/IGF-I axis in renal development.

An intact renin-angiotensin system is a prerequisite for normal renal development

All components of the renin-angiotensin system (RAS) are highly expressed in the developing kidney in a pattern that suggests a role for angiotensin II in renal development In support of this notion, pharmacological interruption of angiotensin II type-1 (AT1) receptor-mediated effects in animals with an ongoing nephrogenesis produces specific renal abnormalities characterized by papillary atrophy, abnormal wall thickening of intrarenal arterioles, tubular atrophy associated with expansion of the interstitium, and a marked impairment in urinary concentrating ability. Similar changes in renal morphology and function also develop in mice with targeted inactivation of the genes that encode angiotensinogen, angiotensin converting enzyme, or both AT1 receptor isoforms simultaneously. Taken together, these results clearly indicate that an intact signalling through AT1 receptors is a prerequisite for normal renal development In a recent study, an increased incidence of congenital anomalies of the kidney and urinary tract was detected in mice deficient in the angiotensin II type-2 receptor, suggesting that this receptor subtype is also involved in the development of the genitourinary tract The present report mainly reviews the renal abnormalities that have been induced by blocking the RAS pharmacologically or by gene targeting in experimental animal models. In addition, pathogenetic mechanisms and clinical implications are discussed.

Postnatal time frame for renal vulnerability to enalapril in rats

Angiotensin-converting enzyme inhibition or angiotensin II type 1 receptor blockade in neonatal, but not in weaned, rats induces irreversible renal histologic abnormalities and an impaired urinary concentrating ability. The aim of the present study was to define the postnatal time frame when the rat kidney is vulnerable to an interruption of the renin-angiotensin system. Male Wistar rats received daily injections of enalapril (10 mg/kg, intraperitoneally) during different age intervals within 3 to 24 d,of age. Fluid handling and urinary concentrating ability, renal function under pentobarbital anesthesia, and kidney histology using stereologic techniques were evaluated in adult rats. Enalapril treatment within 3 to 13 d after birth induced abnormalities in renal function and morphology long-term, whereas treatment initiated at 14 d of age did not. The main histologic alterations were papillary atrophy, and a reduction in the volume of tubular epithelial cells in association with an increase in the proportion of interstitium, throughout the cortex and outer medulla. Functionally, the predominant defect was an impairment in urinary concentrating ability, which correlated with the degree of papillary atrophy. In conclusion, the vulnerable age interval for the induction of irreversible renal abnormalities by enalapril was the first 13 d after birth in the rat. This postnatal time span coincides with the completion of nephrogenesis and a period of marked tubular growth and differentiation, suggesting a pivotal role for angiotensin II in these processes.

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

ANG II is known to be important in normal renal development, but the long-term consequences of a suppressed renin-angiotensin system (RAS) during the developmental period are not completely understood. This study tested the hypothesis that the RAS in the developing animal is important in long-term regulation of renal function and arterial pressure. Newborn Sprague-Dawley rat pups were given the ANG II AT1 receptor antagonist losartan (25 mg . kg-1 . day-1 sc) for the first 12 days of postnatal life (Los). Body weights at weaning (22 days) were significantly reduced in Los (53.4 +/- 3.2 vs. 64.5 +/- 3.6 g in controls); however, at the time of study (approximately 22 wk), body weights and the kidney-to-body weight ratios were not different. In chronically instrumented conscious animals, glomerular filtration rate and effective renal plasma flow were reduced by 27 and 20%, respectively, in Los; the filtration fraction was not different. Maximal urine concentrating ability was also reduced in Los (1,351 +/- 45 vs. 2,393 +/- 52 mosmol/kg in controls). Mean arterial pressure was significantly higher in Los (134 +/- 3 vs. 120 +/- 1 mmHg). The number of glomeruli per kidney was reduced by 42% in Los, but the total glomerular volume was unchanged. Thus perinatal blockade of ANG II AT1 receptors results in fewer but enlarged glomeruli, reduced renal function, and an increased arterial pressure in adulthood. These data indicate that perinatal ANG II, acting via AT1 receptors, plays an important role in renal development and long-term control of renal function and arterial pressure. Physiological conditions that cause suppression of the RAS in the developing animal may have long-term consequences for renal function and blood pressure.

Role of angiotensin in renal vascular development

All components of the renin-angiotensin system (RAS) are expressed in the developing kidney in a temporospatial pattern that suggests a role for this system in kidney morphogenesis. Pharmacological blockade of angiotensin actions in fetal and newborn animals results in striking alterations in kidney architecture, including immature glomeruli and papillae, dilated tubuli, and arrested vascular development. Inactivation of angiotensinogen or angiotensin converting enzyme genes in mice results in similar anomalies that begin as subtle alterations in early life and become more pronounced as extrauterine life progresses. However, inactivation of each angiotensin receptor subtype does not result in obvious morphological abnormalities, suggesting functional redundancy at the receptor level. Crossing of mice lacking the various receptor subtypes should be revealing. Overall, the available information suggests that the RAS is necessary for the normal morphological and functional development of the kidney and the preservation of kidney architecture in adult life.

Genetic deficiency of angiotensinogen produces an impaired urine concentrating ability in mice

Angiotensinogen gene-knockout (Atg-/-) mice lacking angiotensin II exhibit chronic hypotension. The present study was designed to investigate pathophysiology of Atg-/- mice from the renal functional view. Wild-type (Atg+/+) and Atg-/- mice at 10 weeks of age were housed in metabolic cages for 24-hour urine collection. When provided free access to water, Atg-/- mice showed an increased urine output and a decreased urine osmolality compared with Atg+/+ mice. Urinary excretion and plasma levels of vasopressin were significantly higher in mutant mice than in wild-type mice. On the other hand, urinary excretion of aldosterone in mutant mice was suppressed to the levels under the detection limit of the assay system. The mean plasma aldosterone level of Atg-/- mice was suppressed to 30% of that of Atg+/+ mice. Plasma levels of creatinine, endogenous creatinine clearance, and urinary electrolyte excretion were not different between these mice. In Atg+/+ mice, urine osmolality was markedly increased from 1929 +/- 21 to 3314 +/- 402 mOsm/kg during water deprivation, whereas this parameter in Atg-/- mice did not change significantly (from 1413 +/- 121 to 1590 +/- 92 mOsm/kg). Urinary vasopressin excretion increased during water deprivation from 0.24 +/- 0.04 and 0.70 +/- 0.08 to 0.42 +/- 0.06 and 2.31 +/- 0.35 ng/mg creatinine in wild-type and mutant mice, respectively. Histologic study revealed interstitial inflammation, and atrophic changes in the tubules and papilla in Atg-/- mice. In conclusion, a genetic deficiency of angiotensinogen produced an impaired urine concentrating ability and tubulointerstitial lesions, indicating the critical role of angiotensinogen in developing normal tubular function and construction.

Neonatal angiotensin-converting enzyme inhibition in the rat induces persistent abnormalities in renal function and histology

Recently, we reported that neonatal blockade of the renin-angiotensin system in the rat produces irreversible abnormalities in renal histology associated with increased diuresis. In the present study, we assessed the long-term consequences of neonatal angiotensin-converting enzyme inhibition on renal function. Rats were injected with 10 mg.kg-1.d-1 enalapril or vehicle from day 3 to day 24 after birth. Urine concentrating ability, renal function, and renal histology were assessed in 16-week-old rats. There was a twofold increase in diuresis and water intake in enalapril-treated rats throughout the study course. Urine osmolality after 24 hours of water deprivation was 1008 +/- 108 and 2549 +/- 48 mOsm.kg-1 (P < .05) in enalapril- and vehicle-treated rats, respectively. Glomerular filtration rate (0.54 +/- 0.03 versus 0.75 +/- 0.06 mL.min-1x100 g body wt-1, P < .05) and effective renal plasma flow (1.76 +/- 0.09 versus 2.19 +/- 0.14 mL.min-1x100 g body wt-1, P < .05) were reduced in neonatally enalapril-treated versus control rats. Absolute and fractional urinary sodium excretion values were elevated (P < .05) in enalapril-treated rats. Semiquantitative assessment of renal histology demonstrated statistically significant degrees of papillary atrophy, interstitial fibrosis and inflammation, tubular atrophy and dilatation, and focal glomerulosclerosis in neonatally enalapril-treated rats. In conclusion, neonatal angiotensin-converting enzyme inhibition in the rat produces irreversible alterations in renal function and morphology, demonstrating the importance of an intact renin-angiotensin system neonatally for normal renal development.

Toxicokinetic analysis of losartan during gestation and lactation in the rat

Previous developmental and reproductive toxicity studies in rats with losartan, a potent AT1-selective angiotensin II (AII) receptor antagonist, correlated maternal treatment during gestation day (GD) 15-20 with irreversible renal abnormalities in the F1 generation (Spence et al., '95a,b). Continued treatment through lactation was also associated with increases in pup mortality and decreases in pup body weights that persisted through weaning. The studies presented here were undertaken to quantify fetal and neonatal exposure to losartan when administered to the dam by oral gavage during early gestation, late gestation, and lactation. Following daily oral dosing of 135 mg/kg/day on GD6-15, fetal drug levels were negligible. However, losartan and its active metabolite, EXP3174 (L-158,641) were readily detectable in fetal plasma on GD 20 (estimated AUC values, 50.70 and 167.70 micrograms/hr/ml, respectively) and maternal milk during lactation (1.61 and 1.67 micrograms/ml, respectively). These studies suggest that the relative increased sensitivity of the fetus as compared to the neonate for losartan-induced renal lesions is related to the degree of exposure which is dependent on the time of administration (early gestation vs. late gestation/lactation) and the route of exposure (transplacental or through the milk). Furthermore, the maximum exposure to losartan and EXP3174 correlates with the ontogeny of the renin angiotensin system on approximately GD 17 and the critical period for losartan-induced renal lesions (GD15-20). The data support the hypothesis that the observed adverse fetal and neonatal effects are pharmacologically mediated, presumably through the lack of AT1 receptor stimulation.

Evaluation of the reproductive and developmental toxicity of the AT1-selective angiotensin II receptor antagonist losartan in rats

Losartan, an AT1-selective angiotensin II receptor antagonist, was evaluated in female rats for effects on fertility, reproduction, and perinatal and postnatal development. In a range-finding study, pregnant rats were treated orally from gestation days 6-17 (GD 6-17) with doses of 25, 75, 150, 225, and 300 mg Losartan/kg/day. There were treatment-related decreases in maternal body weight gain, slight treatment-related decreases in hemoglobin concentration, and slight treatment-related increases in serum urea nitrogen in the 225 and 300 mg/kg/day groups. In a fertility study, female rats were treated for 15 days prior to mating, during mating, and GD 0-19 with doses of 25, 100, and 300 mg Losartan/kg/day. The initial dose of 300 mg/kg/day was lowered to 200 mg/kg/day at the start of mating due to excessive body weight loss during the premating treatment interval. There were no treatment-related effects on reproductive performance, mating, or fertility indices in the F0 generation. There was no evidence of treatment-related or dose-related fetal malformations. However, decreased F1 pup body weights were observed in all drug-treated groups. In the 100 and 300/200 mg/kg/day groups there were treatment-related increases in F1 pup mortality and alterations in the pattern of postweaning body weight gains. There was also a delay in developmental signs in the 100 and 300/200 mg/kg/day groups, which were likely secondary to the decreased weight of the pups in these groups. In a developmental toxicity study, pregnant rats were administered 50, 100, and 200 mg Losartan/kg/day on GD 6-17. There was no evidence of developmental toxicity in any dose group. Maternal toxicity was evident in the 200 mg/kg/day group as a treatment-related decrease in body weight gain during gestation. In a late-gestation/lactation study, pregnant rats were administered 10, 25, and 100 mg Losartan/kg/day on GD 15 through lactation day 20 (LD 20). There were treatment-related decreases in maternal body weight gain during gestation and lactation in the 100 mg/kg/day group. Decreased pup weights were noted in all dose groups, and pre- and postweaning pup deaths were observed in the high dose group which were comparable to those observed in the female fertility study. The lack of fetal body weight effects at 100 mg Losartan/kg/day in the developmental toxicity study, with treatment ending on GD 17, indicates that adverse effects observed in the F1 generation in the fertility and late-gestation/lactation studies were due to exposure during late gestation and/or lactation.(ABSTRACT TRUNCATED AT 400 WORDS)