Persistent anuria, neonatal death, and renal microcystic lesions after prenatal exposure to indomethacin

Drug-induced fetal and offspring disorders, beyond birth defects

Studies on drug utilization in western countries disclosed that about nine over ten women use at least one or more drugs during pregnancy. Determining whether a drug is safe or not in pregnant women is a challenge of all times. As a developing organism, the fetus is particularly vulnerable to effects of drugs used by the mother. Historically, research has predominantly focused on birth defects, which represent the most studied adverse pregnancy outcomes. However, drugs can also alter the ongoing process of pregnancy and impede the general growth of the fetus. Finally, adverse drug reactions can theoretically damage all developing systems, organs or tissues, such as the central nervous system or the immune system. This extensive review focuses on different aspects of drug-induced damages affecting the fetus or the newborn/infant, beyond birth defects, which are not addressed here.

Trends in harmful drug exposure during pregnancy in France between 2013 and 2019: A nationwide cohort study

OBJECTIVE

Describe the trends of exposure to harmful drugs during pregnancy over recent years in France.

DESIGN

Nationwide cohort study.

SETTING

The French National administrative health Data System (SNDS).

POPULATION

Pregnancies starting between 2013 and 2019 and outcomes corresponding to live births, medical terminations of pregnancy, and stillbirths.

METHODS

Each pregnancy was divided into a preconceptional period of 90 days before conception and three trimesters from conception to birth. Harmful drugs were defined according to their risks to the fetus: teratogenicity or fetotoxicity. Exposure was defined using the critical period during pregnancy for each type of harmful drug: preconceptional period or first trimester for teratogenic drugs and second or third trimesters for fetotoxic drugs.

MAIN OUTCOME MEASURES

Prevalence of pregnancies exposed to at least one harmful drug.

RESULTS

Among 5,253,284 pregnancies, 204,402 (389 per 10,000) pregnancies were exposed to at least one harmful drug during the critical periods: 48,326 (92 per 10,000) pregnancies were exposed to teratogenic drugs during the preconceptional period or the first trimester, and 155,514 (299 per 10,000) pregnancies were exposed to fetotoxic drugs during the second or third trimesters. Teratogenic drugs were mainly retinoids for topical use (44 per 10,000 pregnancies), antiepileptics (13 per 10,000 pregnancies) and statins (13 per 10,000 pregnancies). Fetotoxic drugs were mainly non-steroidal anti-inflammatory drugs (NSAIDs), for systemic (128 per 10,000 pregnancies) and topical use (122 per 10,000 pregnancies). Exposure to teratogenic drugs decreased from the preconceptional period to the first trimester. Exposure to fetotoxic drugs decreased from the second to the third trimester. Between 2013 and 2019, we found a decrease in harmful drug exposure overall, mainly for topical and systemic NSAIDs and for topical retinoids.

CONCLUSIONS

In this nationwide study, about one in 25 pregnancies was exposed to at least one harmful drug, mainly NSAIDs and topical retinoids. Although the prevalence of harmful drug exposure decreased over the study period, NSAID exposure in the second and third trimester remains of concern.

Kidney Angiotensin in Cardiovascular Disease: Formation and Drug Targeting

The concept of local formation of angiotensin II in the kidney has changed over the last 10-15 years. Local synthesis of angiotensinogen in the proximal tubule has been proposed, combined with prorenin synthesis in the collecting duct. Binding of prorenin via the so-called (pro)renin receptor has been introduced, as well as megalin-mediated uptake of filtered plasma-derived renin-angiotensin system (RAS) components. Moreover, angiotensin metabolites other than angiotensin II [notably angiotensin-(1-7)] exist, and angiotensins exert their effects via three different receptors, of which angiotensin II type 2 and Mas receptors are considered renoprotective, possibly in a sex-specific manner, whereas angiotensin II type 1 (AT1) receptors are believed to be deleterious. Additionally, internalized angiotensin II may stimulate intracellular receptors. Angiotensin-converting enzyme 2 (ACE2) not only generates angiotensin-(1-7) but also acts as coronavirus receptor. Multiple, if not all, cardiovascular diseases involve the kidney RAS, with renal AT1 receptors often being claimed to exert a crucial role. Urinary RAS component levels, depending on filtration, reabsorption, and local release, are believed to reflect renal RAS activity. Finally, both existing drugs (RAS inhibitors, cyclooxygenase inhibitors) and novel drugs (angiotensin receptor/neprilysin inhibitors, sodium-glucose cotransporter-2 inhibitors, soluble ACE2) affect renal angiotensin formation, thereby displaying cardiovascular efficacy. Particular in the case of the latter three, an important question is to what degree they induce renoprotection (e.g., in a renal RAS-dependent manner). This review provides a unifying view, explaining not only how kidney angiotensin formation occurs and how it is affected by drugs but also why drugs are renoprotective when altering the renal RAS. SIGNIFICANCE STATEMENT: Angiotensin formation in the kidney is widely accepted but little understood, and multiple, often contrasting concepts have been put forward over the last two decades. This paper offers a unifying view, simultaneously explaining how existing and novel drugs exert renoprotection by interfering with kidney angiotensin formation.

Intact prostaglandin signaling through EP2 and EP4 receptors in stromal progenitor cells is required for normal development of the renal cortex in mice

Cyclooxygenase (Cox) inhibitors are known to have severe side effects during renal development. These consist of reduced renal function, underdeveloped subcapsular glomeruli, interstitial fibrosis, and thinner cortical tissue. Global genetic deletion of Cox-2 mimics the phenotype observed after application of Cox inhibitors. This study aimed to investigate which cell types express Cox-2 and prostaglandin E2 receptors and what functions are mediated through this pathway during renal development. Expression of EP2 and EP4 mRNA was detected by RNAscope mainly in descendants of FoxD1+ stromal progenitors; EP1 and EP3, on the other hand, were expressed in tubules. Cox-2 mRNA was detected in medullary interstitial cells and macula densa cells. Functional investigations were performed with a cell-specific approach to delete Cox-2, EP2, and EP4 in FoxD1+ stromal progenitor cells. Our data show that Cox-2 expression in macula densa cells is sufficient to drive renal development. Deletion of EP2 or EP4 in FoxD1+ cells had no functional effect on renal development. Codeletion of EP2 and EP4 in FoxD1+ stromal cells, however, led to severe glomerular defects and a strong decline of glomerular filtration rate (1.316 ± 69.7 µL/min/100 g body wt in controls vs. 644.1 ± 64.58 µL/min/100 g body wt in FoxD1+/Cre EP2-/- EP4ff mice), similar to global deletion of Cox-2. Furthermore, EP2/EP4-deficient mice showed a significant increase in collagen production with a strong downregulation of renal renin expression. This study shows the distinct localization of EP receptors in mice. Functionally, we could identify EP2 and EP4 receptors in stromal FoxD1+ progenitor cells as essential receptor subtypes for normal renal development.NEW & NOTEWORTHY Cyclooxygenase-2 (Cox-2) produces prostaglandins that are essential for normal renal development. It is unclear in which cells Cox-2 and the receptors for prostaglandin E2 (EP receptors) are expressed during late nephrogenesis. This study identified the expression sites for EP subtypes and Cox-2 in neonatal mouse kidneys. Furthermore, it shows that stromal progenitor cells may require intact prostaglandin E2 signaling through EP2 and EP4 receptors for normal renal development.

A Multiparametric Assay Platform for Simultaneous In Vivo Assessment of Pronephric Morphology, Renal Function and Heart Rate in Larval Zebrafish

Automated high-throughput workflows allow for chemical toxicity testing and drug discovery in zebrafish disease models. Due to its conserved structural and functional properties, the zebrafish pronephros offers a unique model to study renal development and disease at larger scale. Ideally, scoring of pronephric phenotypes includes morphological and functional assessments within the same larva. However, to efficiently upscale such assays, refinement of existing methods is required. Here, we describe the development of a multiparametric in vivo screening pipeline for parallel assessment of pronephric morphology, kidney function and heart rate within the same larva on a single imaging platform. To this end, we developed a novel 3D-printed orientation tool enabling multiple consistent orientations of larvae in agarose-filled microplates. Dorsal pronephros imaging was followed by assessing renal clearance and heart rates upon fluorescein isothiocyanate (FITC)-inulin microinjection using automated time-lapse imaging of laterally positioned larvae. The pipeline was benchmarked using a set of drugs known to induce developmental nephrotoxicity in humans and zebrafish. Drug-induced reductions in renal clearance and heart rate alterations were detected even in larvae exhibiting minor pronephric phenotypes. In conclusion, the developed workflow enables rapid and semi-automated in vivo assessment of multiple morphological and functional parameters.

Risk estimation of fetal adverse effects after short-term second trimester exposure to non-steroidal anti-inflammatory drugs: a literature review

PURPOSE

Non-steroidal anti-inflammatory drugs (NSAIDs) are not recommended in the 3rd trimester of pregnancy due to known fetal adverse effects in an advanced gestational age. This investigation was performed to assess whether there is a significant risk of NSAIDs being used as an analgesic or antipyretic medication in the 2nd trimester.

METHODS

A systematic search for publications reporting 2nd trimester NSAID exposure was performed in MEDLINE. The search focused on case descriptions reporting defined adverse effects including prenatal ductus arteriosus constriction, oligohydramnios, neonatal renal failure, and primary pulmonary hypertension. Original articles published until February 2018 were considered for evaluation.

RESULTS

Out of 681 identified publications, 26 included relevant information on the defined adverse effects. Among these publications, premature labor was the major reason for 2nd trimester indomethacin treatment while other clinical indications and other NSAIDs were underrepresented. Narrowing or closure of the ductus arteriosus in the 2nd trimester was described in 33 fetuses. Only eight publications reported adverse effects after less than 7-day exposure during the 2nd trimester.

CONCLUSIONS

Based on these results, short-term use of NSAIDs as analgesics or antipyretics in the 2nd trimester does not appear to pose a substantial risk for fetal adverse effects. Long-term use in the late 2nd trimester, however, should always be monitored.

Comparative effect of indomethacin (IndoM) on the enzymes of carbohydrate metabolism, brush border membrane and oxidative stress in the kidney, small intestine and liver of rats

Indomethacin (IndoM) has prominent anti-inflammatory and analgesic-antipyretic properties. However, high incidence and severity of side-effects on the structure and functions of the kidney, liver and intestine limits its clinical use. The present study tested the hypothesis that IndoM causes multi-organ toxicity by inducing oxidative stress that alters the structure of various cellular membranes, metabolism and hence functions. The effect of IndoM was determined on the enzymes of carbohydrate metabolism, brush border membrane (BBM) and oxidative stress in the rat kideny, liver and intestine to understand the mechanism of IndoM induced toxicity. Adult male Wister rats were given IndoM (20 mg/kg) intra-peritoneally in sodium bicarbonate twice a day for 3 d. The body weights of the rats were recorded before and after experimental procedure. IndoM administration significantly increased blood urea nitrogen, serum creatinine, cholesterol and alkaline phosphatase but inorganic phosphate indicating IndoM induced renal, hepatic and intestinal toxicity. Activity of lactate dehydrogenase along with glucose-6- and fructose-1, 6-bis phosphatase, glucose-6-phosphate dehydrogenase and NADP-malic enzyme increased but malate dehydrogenase decreased in all tissues. Lipid peroxidation (LPO) significantly increased whereas the antioxidant enzymes decreased in all rat tissues studied. The results indicate that IndoM administration caused severe damage to kidney, liver and intestine by icreasing LPO, suppressing antioxidant enzymes and inhibiting oxidative metablolism. The energy dependence was shifted to anaerobic glycolysis due to mitochondrial damage supported by increased gluconeogenesis to provide more glucose to meet energy requirements.

Fetal anhydramnios following maternal non-steroidal anti-inflammatory drug use in pregnancy

We present a case report of transient fetal anhydramnios following maternal non-steroidal anti-inflammatory drug use in pregnancy. This reduction in liquor volume resolved following cessation of the medication with no obvious ill-effect on neonatal outcome. The case report is followed by a comprehensive summary of the relevant literature.

Salt supplementation ameliorates developmental kidney defects in COX-2−/− mice

Deficiency of cyclooxygenase-2 (COX-2) activity in the early postnatal period causes impairment of kidney development leading to kidney insufficiency. We hypothesize that impaired NaCl reabsorption during the first days of life is a substantial cause for nephrogenic defects observed in COX-2−/− mice and that salt supplementation corrects these defects. Daily injections of NaCl (0.8 mg·g−1·day−1) for the first 10 days after birth ameliorated impaired kidney development in COX-2−/− pups resulting in an increase in glomerular size and fewer immature superficial glomeruli. However, impaired renal subcortical growth was not corrected. Increasing renal tubular flow by volume load or injections of KCl did not relieve the renal histomorphological damage. Administration of torsemide and spironolactone also affected nephrogenesis resulting in diminished glomeruli and cortical thinning. Treatment of COX-2−/− pups with NaCl/DOCA caused a stronger mitigation of glomerular size and induced a slight but significant growth of cortical tissue mass. After birth, renal mRNA expression of NHE3, NKCC2, ROMK, NCCT, ENaC, and Na+/K+-ATPase increased relative to postnatal day 2 in wild-type mice. However, in COX-2−/− mice, a significantly lower expression was observed for NCCT, whereas NaCl/DOCA treatment significantly increased NHE3 and ROMK expression. Long-term effects of postnatal NaCl/DOCA injections indicate improved kidney function with normalization of pathologically enhanced creatinine and urea plasma levels; also, albumin excretion was observed. In summary, we present evidence that salt supplementation during the COX-2-dependent time frame of nephrogenesis partly reverses renal morphological defects in COX-2−/− mice and improves kidney function.

Acetylsalicylic acid interferes with embryonic kidney growth and development by a prostaglandin-independent mechanism

AIM

To evaluate the effects of the non-selective, non-steroidal anti-inflammatory drug (NSAID) acetylsalicylic acid (ASA), on ex vivo embryonic kidney growth and development.

METHODS

Pairs of fetal mouse kidneys at embryonic day 12.5 were cultured ex vivo in increasing concentrations of ASA (0.04-0.4 mg/mL) for up to 7 d. One organ from each pair was grown in control media and was used as the internal control for the experimental contralateral organ. In some experiments, organs were treated with ASA for 48 h and then transferred either to control media alone or control media containing 10 μmol/L prostaglandin E₂ (PGE₂) for a further 5 d. Fetal kidneys were additionally obtained from prostaglandin synthase 2 homozygous null or heterozygous (PTGS2^-/- and PTGS2^-/+) embryos and grown in culture. Kidney cross-sectional area was used to determine treatment effects on kidney growth. Whole-mount labelling to fluorescently detect laminin enabled crude determination of epithelial branching using confocal microscopy.

RESULTS

Increasing ASA concentration (0.1, 0.2 and 0.4 mg/mL) significantly inhibited metanephric growth (P < 0.05). After 7 d of culture, exposure to 0.2 mg/mL and 0.4 mg/mL reduced organ size to 53% and 23% of control organ size respectively (P < 0.01). Addition of 10 μmol/L PGE₂ to culture media after exposure to 0.2 mg/mL ASA for 48 h resulted in a return of growth area to control levels. Application of control media alone after cessation of ASA exposure showed no benefit on kidney growth. Despite the apparent recovery of growth area with 10 μmol/L PGE₂, no obvious renal tubular structures were formed. The number of epithelial tips generated after 48 h exposure to ASA was reduced by 40% (0.2 mg/mL; P < 0.05) and 47% (0.4 mg/mL; P < 0.01). Finally, growth of PTGS2^-/- and PTGS2^+/- kidneys in organ culture showed no differences, indicating that PTGS2 derived PGE₂ may at best have a minor role.

CONCLUSION

ASA reduces early renal growth and development but the role of prostaglandins in this may be minor.

Angiotensin II-AT1-receptor signaling is necessary for cyclooxygenase-2-dependent postnatal nephron generation

Deletion of cyclooxygenase-2 (COX-2) causes impairment of postnatal kidney development. Here we tested whether the renin angiotensin system contributes to COX-2-dependent nephrogenesis in mice after birth and whether a rescue of impaired renal development and function in COX-2^-/- mice was achievable. Plasma renin concentration in mouse pups showed a birth peak and a second peak around day P8 during the first 10 days post birth. Administration of the angiotensin II receptor AT1 antagonist telmisartan from day P1 to P3 did not result in cortical damage. However, telmisartan treatment from day P3 to P8, the critical time frame of renal COX-2 expression, led to hypoplastic glomeruli, a thinned subcapsular cortex and maturational arrest of superficial glomeruli quite similar to that observed in COX-2^-/- mice. In contrast, AT2 receptor antagonist PD123319 was without any effect on renal development. Inhibition of the renin angiotensin system by aliskiren and enalapril caused similar glomerular defects as telmisartan. Administration of the AT1 receptor agonist L162313 to COX-2^-/- pups improved kidney growth, ameliorated renal defects, but had no beneficial effect on reduced cortical mass. L162313 rescued impaired renal function by reducing serum urea and creatinine and mitigated pathologic albumin excretion. Moreover, glomerulosclerosis in the kidneys of COX-2^-/- mice was reduced. Thus, angiotensin II-AT1-receptor signaling is necessary for COX-2-dependent normal postnatal nephrogenesis and maturation.

Prostaglandin signaling regulates nephron segment patterning of renal progenitors during zebrafish kidney development

Kidney formation involves patterning events that induce renal progenitors to form nephrons with an intricate composition of multiple segments. Here, we performed a chemical genetic screen using zebrafish and discovered that prostaglandins, lipid mediators involved in many physiological functions, influenced pronephros segmentation. Modulating levels of prostaglandin E2 (PGE₂) or PGB₂ restricted distal segment formation and expanded a proximal segment lineage. Perturbation of prostaglandin synthesis by manipulating Cox1 or Cox2 activity altered distal segment formation and was rescued by exogenous PGE₂. Disruption of the PGE₂ receptors Ptger2a and Ptger4a similarly affected the distal segments. Further, changes in Cox activity or PGE₂ levels affected expression of the transcription factors irx3b and sim1a that mitigate pronephros segment patterning. These findings show for the first time that PGE₂ is a regulator of nephron formation in the zebrafish embryonic kidney, thus revealing that prostaglandin signaling may have implications for renal birth defects and other diseases.

DOI:http://dx.doi.org/10.7554/eLife.17551.001

COX-2 gene dosage-dependent defects in kidney development

Deletion of cyclooxygenase (COX)-2 causes impairment of kidney development, including hypothrophic glomeruli and cortical thinning. A critical role for COX-2 is seen 4-8 days postnatally. The present study was aimed at answering whether different COX-2 gene dosage and partial pharmacological COX-2 inhibition impairs kidney development. We studied kidney development in COX-2(+/+), COX-2(+/-), and COX-2(-/-) mice as well as in C57Bl6 mice treated postnatally with low (5 mg·kg(-1)·day(-1)) and high (10 mg·kg(-1)·day(-1)) doses of the selective COX-2 inhibitor SC-236. COX-2(+/-) mice exhibit impaired kidney development leading to reduced glomerular size but, in contrast to COX-2(-/-) mice, only marginal cortical thinning. Moreover, in COX-2(+/-) and COX-2(-/-) kidneys, juxtamedullary glomeruli, which develop in the very early stages of nephrogenesis, also showed a size reduction. In COX-2(+/-) kidneys at the age of 8 days, we observed significantly less expression of COX-2 mRNA and protein and less PGE2 and PGI2 synthetic activity compared with COX-2(+/+) kidneys. The renal defects in COX-2(-/-) and COX-2(+/-) kidneys could be mimicked by high and low doses of SC-236, respectively. In aged COX-2(+/-) kidneys, glomerulosclerosis was observed; however, in contrast to COX-2(-/-) kidneys, periglomerular fibrosis was absent. COX-2(+/-) mice showed signs of kidney insufficiency, demonstrated by enhanced serum creatinine levels, quite similar to COX-2(-/-) mice, but, in contrast, serum urea remained at the control level. In summary, function of both COX-2 gene alleles is absolutely necessary to ensure physiological development of the mouse kidney. Loss of one copy of the COX-2 gene or partial COX-2 inhibition is associated with distinct renal damage and reduced kidney function.

Long-term renal consequences of preterm birth

The normal development of the kidney may be affected by several factors, including abnormalities in placental function, resulting in fetal growth restriction, exposure to maternal disease states, including hypertension and diabetes, antenatal steroids, chorioamnionitis, and preterm delivery. After preterm birth, several further insults may occur that may influence nephrogenesis and renal health, including exposure to nephrotoxic medications, postnatal growth failure, and obesity after growth restriction. In this review article, common clinical neonatal scenarios are used to highlight these renal risk factors, and the animal and human evidence on which these risk factors are based are discussed.

Postnatal regulation of 15-hydroxyprostaglandin dehydrogenase in the rat kidney

Cyclooxygenase 2 (COX-2) has an established role in postnatal kidney development. 15-Hydroxyprostaglandin dehydrogenase (15-PGDH) is recently identified as an endogenous inhibitor of COX-2, limiting the production of COX-2-derived prostanoids in several pathological conditions. The present study was undertaken to examine the regulation of renal 15-PGDH expression during postnatal kidney development in rats compared with COX-2. qRT-PCR and immunoblotting demonstrated that 15-PGDH mRNA and protein in the kidney were present in neonates, peaked in the second postnatal week, and then declined sharply to very low level in adulthood. Immunostaining demonstrated that at the second postnatal week, renal 15-PGDH protein was predominantly found in the proximal tubules stained positive for Na/H exchanger 3 and brush borders (periodic acid-Schiff), whereas COX-2 protein was restricted to macular densa and adjacent thick ascending limbs. Interestingly, in the fourth postnatal week, 15-PGDH protein was redistributed to thick ascending limbs stained positive for the Na-K-2Cl cotransporter. After 6 wk of age, 15-PGDH protein was found in the granules in subsets of the proximal tubules. Overall, these results support a possibility that 15-PGDH may regulate postnatal kidney development through interaction with COX-2.

Temporal expression of the PGE2 synthetic system in the kidney is associated with the time frame of renal developmental vulnerability to cyclooxygenase-2 inhibition

Pharmacological blockade of cyclooxygenase-2 (COX-2) causes impairment of kidney development. The present study was aimed at determining temporal expression pattern and activity of the PGE(2) synthetic pathway during postnatal nephrogenesis in mice and its association to the time window sensitive to COX-2 inhibition. During the first 10 days after birth, we observed transient induction of mRNA and protein for microsomal PGE synthase (mPGES)-1 between postnatal days 4 (P4) and P8, but not for mPGES-2 or cytosolic PGE synthase (cPGES). PGE(2) synthetic activity using arachidonic acid and PGH(2) as substrates and also urinary excretion of PGE(2) were enhanced during this time frame. In parallel to the PGE(2) system, COX-2 but not COX-1 expression was also transiently induced. Studying glomerulogenesis in EP receptor knockout mice revealed a reduction in glomerular size in EP1(-/-), EP2(-/-), and EP4(-/-) mice, supporting the developmental role of PGE(2). The most vulnerable time window to COX-2 inhibition by SC-236 was found closely related to the temporal expression of COX-2 and mPGES-1. The strongest effects of COX-2 inhibition were achieved following 8 days of drug administration. Similar developmental damage was caused by application of rofecoxib, but not by the COX-1-selective inhibitor SC-560. COX-2 inhibition starting after P10 has had no effect on the size of glomeruli or on the relative number of superficial glomeruli; however, growth of the renal cortex was significantly diminished, indicating the requirement of COX-2 activity after P10. Effects of COX-2 inhibition on renal cell differentiation and on renal fibrosis needed a prolonged time of exposition of at least 10 days. In conclusion, temporal expression of the PGE(2) synthetic system coincides with the most vulnerable age interval for the induction of irreversible renal abnormalities. We assume that mPGES-1 is coregulated with COX-2 for PGE(2) synthesis to orchestrate postnatal kidney development and growth.

Effects of ibuprofen treatment on the developing preterm baboon kidney

Preterm neonates are commonly exposed postnatally to pharmacological treatments for a patent ductus arteriosus. Exposure of the developing kidney to nephrotoxic medications may adversely impact renal development. This study aimed to determine the effect of early postnatal ibuprofen treatment, both alone and in combination with a nitric oxide synthase inhibitor (NOSi), on renal development and morphology. Baboon neonates were delivered prematurely at 125-day (125d) gestation (term = 185d) and were euthanized at birth or postnatal day 6. Neonates were divided into four groups: 125d gestational controls (n = 8), Untreated (n = 8), Ibuprofen (n = 6), and ibuprofen (Ibu)+NOSi (n = 4). Animals in the Ibuprofen and Ibu+NOSi groups received five doses of ibuprofen, with the Ibuprofen+NOSi animals additionally administered a NOS inhibitor (N(G)-monomethyl-l-arginine). There was no difference among groups in body weight, kidney weight, or glomerular generation number. Nephrogenic zone width was significantly reduced in the Ibuprofen group (123.5 ± 7.4 μm) compared with the 125d gestational control (176.1 ± 6.9 μm) and Untreated animals (169.7 ± 78.8 μm). In the Ibu+NOSi group, nephrogenic zone width averaged 152.7 ± 3.9 μm, which was not significantly different from any other group. Morphologically abnormal glomeruli were present at a range of 0.0-22.9% in the Untreated group, 0.0-6.1% in the Ibuprofen group, and 0.0-1.4% in the Ibu+NOSi group. In conclusion, early postnatal ibuprofen exposure is associated with a reduced nephrogenic zone width, which may suggest the early cessation of nephrogenesis following treatment. Ultimately, this may impact the number of nephrons formed in the preterm kidney.

Effects of ibuprofen treatment on the developing preterm baboon kidney

Preterm neonates are commonly exposed postnatally to pharmacological treatments for a patent ductus arteriosus. Exposure of the developing kidney to nephrotoxic medications may adversely impact renal development. This study aimed to determine the effect of early postnatal ibuprofen treatment, both alone and in combination with a nitric oxide synthase inhibitor (NOSi), on renal development and morphology. Baboon neonates were delivered prematurely at 125-day (125d) gestation (term = 185d) and were euthanized at birth or postnatal day 6. Neonates were divided into four groups: 125d gestational controls (n = 8), Untreated (n = 8), Ibuprofen (n = 6), and ibuprofen (Ibu)+NOSi (n = 4). Animals in the Ibuprofen and Ibu+NOSi groups received five doses of ibuprofen, with the Ibuprofen+NOSi animals additionally administered a NOS inhibitor (N(G)-monomethyl-l-arginine). There was no difference among groups in body weight, kidney weight, or glomerular generation number. Nephrogenic zone width was significantly reduced in the Ibuprofen group (123.5 ± 7.4 μm) compared with the 125d gestational control (176.1 ± 6.9 μm) and Untreated animals (169.7 ± 78.8 μm). In the Ibu+NOSi group, nephrogenic zone width averaged 152.7 ± 3.9 μm, which was not significantly different from any other group. Morphologically abnormal glomeruli were present at a range of 0.0-22.9% in the Untreated group, 0.0-6.1% in the Ibuprofen group, and 0.0-1.4% in the Ibu+NOSi group. In conclusion, early postnatal ibuprofen exposure is associated with a reduced nephrogenic zone width, which may suggest the early cessation of nephrogenesis following treatment. Ultimately, this may impact the number of nephrons formed in the preterm kidney.

Defects in mouse nephrogenesis induced by selective and non-selective cyclooxygenase-2 inhibitors

BACKGROUND AND PURPOSE

Deletion of the cyclooxygenase-2 (COX-2) gene causes impairment of kidney development, but the effect of selective inhibitors of COX-2 (coxibs) or the non-selective inhibitors of COX (the classical non-steroidal anti-inflammatory drugs; NSAIDs) on kidney development was less well described.

EXPERIMENTAL APPROACH

We assessed the effects of equipotent analgesic doses of celecoxib, rofecoxib, valdecoxib, etoricoxib and lumiracoxib and of the NSAIDs, diclofenac and naproxen, on postpartum kidney development in mice, from postnatal day 1 (P1) to P21.

KEY RESULTS

All the COX inhibitors, at the doses used, blocked COX-2 activity by more than 80% as assayed by PGE(2) synthesis in lipopolysaccharide-stimulated mouse blood samples. Rofecoxib, etoricoxib and lumiracoxib exerted the most marked impairment of postpartum kidney development, demonstrated by attenuation of kidney growth, reduction in size of glomeruli, increase in immature superficial glomeruli, thinning of subcapsular cortical mass and reduction in size of juxtamedullary glomeruli. These defects were less severe than those in kidneys from COX-2(-/-) mice. Administration of diclofenac and naproxen revealed renal defects similar to those after coxib treatment, but both NSAIDs induced greater arrest of immature superficial glomeruli in the outer cortex and increased the number of undifferentiated proliferating cell nuclear antigen-positive cells. Treatment with celecoxib or valdecoxib caused only minimal changes in renal morphology.

CONCLUSIONS AND IMPLICATIONS

Classical NSAIDs cause similar or even stronger nephrodysgenesis than the coxibs. Also, the ranking of coxibs regarding adverse effects on renal development, using equi-analgesic doses, is rofecoxib = etoricoxib = lumiracoxib > valdecoxib > celecoxib.

Preterm birth and the kidney: implications for long-term renal health

Although the majority of preterm neonates now survive infancy, there is emerging epidemiological evidence to demonstrate that individuals born preterm exhibit an elevated risk for the development of hypertension and renal impairment later in life, thus supporting the developmental origins of health and disease hypothesis. The increased risk may potentially be attributed to a negative impact of preterm birth on nephron endowment. Indeed, at the time when most preterm neonates are delivered, nephrogenesis in the kidney is still ongoing with the majority of nephrons normally formed during the third trimester of pregnancy. A number of clinical studies have provided evidence of altered renal function during the neonatal period, but to date there have been limited studies describing the consequences of preterm birth on kidney structure. Importantly, studies in the preterm baboon have shown that nephrogenesis is clearly ongoing following preterm birth; however, the presence of abnormal glomeruli (up to 18% in some cases) is of concern. Similar glomerular abnormalities have been described in autopsied preterm infants. Prenatal and postnatal factors such as exposure to certain medications, hyperoxia and intrauterine and/or extrauterine growth restriction are likely to have a significant influence on nephrogenesis and final nephron endowment. Further studies are required to determine the factors contributing to renal maldevelopment and to identify potential interventional strategies to maximize nephron endowment at the start of life, thereby optimizing long-term renal health for preterm individuals.

The adverse renal effects of prostaglandin-synthesis inhibition in the fetus and the newborn

OBJECTIVES

To summarize experimental animal data and to provide a limited literature review on the adverse renal effects of nonsteroidal anti-inflammatory drugs (NSAIDs) on the developing fetus and the maturing newborn.

DATA

The experimental data were obtained from anesthetized, ventilated, six- to eight-day-old rabbits that received an intravenous bolus of either acetylsalicylic acid (ASA), ibuprofen (IBU) or indomethacin (INDO). In one set of experiments, ASA was also tested in 12-week-old (young adult) rabbits. Renal function was monitored with inulin and para-aminohippuric acid clearances measuring glomerular filtration rate (GFR) and renal blood flow. The renal vascular resistance was calculated. All three nonspecific cyclo-oxygenase-1 or -2 (COX-1/2) inhibitors caused remarkably similar reversible, oliguric, acute renal failure (ARF). In young adult animals, the side effects were attenuated. The underlying pathophysiology is related to the carefully maintained low GFR of the fetus and the newborn, dependent on a delicate interplay between vasoconstriction (angiotensin II) and vasodilation (prostaglandins [PGs]). When PG-synthesis is inhibited, the vasoconstriction is relatively unopposed, causing ARF.

LITERATURE REVIEW

The renal effects of fetal exposure to NSAIDs are discussed, as are new insights into the role of COX-1/2 for a normal nephrogenesis. COX-nil or COX-inhibited animals have long lasting renal structural injury. Fetuses exposed in utero to significant amounts of NSAIDs have at birth various degrees of renal insufficiency and structural renal defects with a very high mortality.

CONCLUSIONS

All NSAIDs, both specific and nonspecific COX inhibitors, have renal side effects in the immediate post-natal period and should, therefore, be given with the utmost caution. NSAIDs given during pregnancy for the prevention of toxemia, polyhydramnios and premature labour may affect fetal renal function and structure. In animal experiments, IBU was not less nephrotoxic than INDO, as suggested recently by human premature neonates.

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.

The renin-angiotensin system in kidney development: role of COX-2 and adrenal steroids

Recent data from studies in rodents with targeted gene disruption and pharmacological antagonists have shown that the renin-angiotensin-aldosterone system (RAAS) and cyclooxygenase type-2 (COX-2) are necessary for late stages of kidney development. The present review summarizes data on the developmental changes of RAAS and COX-2 and the pathways by which they are activated; their possible interplay and the mechanisms by which they affect kidney development. Intrarenal and circulating renin and angiotensin II (ANG II) are stimulated at birth in most mammals. In rats, renin and ANG II stay significantly elevated in the suckling period while aldosterone stabilizes at an adult level. COX-2 is stimulated in thick ascending limb of Henle's loop in the suckling period at a time when urine concentrating ability is not developed. Data suggest that this induction is mediated by combined low plasma glucocorticoid concentration and by a low NaCl intake. Studies with selective inhibitors of COX-2 and COX-2 null mice show that COX-2 activity stimulates renin secretion from JG-cells during postnatal kidney development and that lack of COX-2 activity leads to pathological change in cortical architecture and eventually to renal failure. In the postnatal period, ANG II initiates and maintains pelvic and ureteric contractions necessary for urine flow. Lack of ANG II in the neonatal period is thought to cause injury by a chronic increase of renal pelvic pressure. Aldosterone is crucial for survival and growth in the neonatal period through its effects on sodium reabsorption and the intrarenal sensitivity to aldosterone is increased in the postnatal period. Final maturation of the kidney occurs through an intimate interplay between a low dietary sodium intake and a non-responsive HPA-axis which stimulates cortical COX-2 activity. COX-2 supports increased activity of the RAAS and may contribute to a low concentrating ability.

Interspecies Differences in the Nephrotoxic Response to Cyclooxygenase Inhibition

In contrast to cyclooxygenase-1 (COX-1), the basal expression of renal cyclooxygenase-2 (COX-2) varies among species. High basal levels of COX-2 in the renal cortex and papilla in dogs compared with monkeys suggest that COX-2 inhibition may lead to distinct nephrotoxic responses. In this study, we compared the renal effects of COX inhibition between dogs and cynomolgus monkeys (n = 6/group) following the administration of naproxen sodium, a non-selective COX-1/COX-2 inhibitor. Dogs and monkeys were treated with 50 or 150 mg/kg/day naproxen sodium, respectively, for 2 to 6 weeks. Naproxen doses used in this study resulted in equivalent inhibition of COX activity in both species as measured by reductions in urinary prostaglandin E2 (PGE2) and 6-keto-PGF1-alpha levels. There was prominent reduction in renal blood flow (43%) and urinary sodium excretion (62%) in dogs but no alterations in renal blood flow and only minimal change (19%) in urinary sodium excretion in monkeys. The canine but not monkey kidney showed prominent COX-2 expression in the macula densa, thick ascending limb of Henle and papillary interstitial cells by immunohistochemistry. After treatment, the canine but not monkey kidneys had mild to moderate renal tubular atrophy and interstitial fibrosis and renal papillary necrosis. Obstructive nephropathy secondary to intra-tubular drug accumulation was seen in monkeys but not in dogs. Collectively, these data demonstrate species differences in the renal response to COX inhibition. The nature of functional and morphologic changes suggests a more prominent role of COX-2 in renal hemodynamics and natriuresis in dogs than in monkeys.

Nimesulide, a cyclooxygenase-2 preferential inhibitor, impairs renal function in the newborn rabbit

Tocolysis with nonsteroidal anti-inflammatory drugs (NSAIDs) has been widely accepted for several years. Recently, the use of the cyclooxygenase-2 (COX2) preferential NSAID nimesulide has been proposed. However, data reporting neonatal acute renal failure or irreversible end-stage renal failure after maternal ingestion of nimesulide question the safety of this drug for the fetus and the neonate. Therefore, this study was designed to define the renal effects of nimesulide in newborn rabbits. Experiments were performed in 28 newborn rabbits. Renal function and hemodynamic parameters were measured using inulin and para-aminohippuric acid clearances as markers of GFR and renal blood flow, respectively. After a control period, nimesulide 2, 20, or 200 microg/kg was given as an i.v. bolus, followed by a 0.05, 0.5, or 5 microg.kg(-1).min(-1) infusion. Nimesulide administration induced a significant dose-dependent increase in renal vascular resistance (29, 37, and 92%, respectively), with a concomitant decrease in diuresis (-5, -23, and -44%), GFR (-12, -23, and -47%), and renal blood flow (-23, -23, and -48%). These results are in contrast with recent reports claiming that selective COX2 inhibition could be safer for the kidney than nonselective NSAIDs. These experiments confirm that prostaglandins, by maintaining renal vasodilation, play a key role in the delicate balance regulating neonatal GFR. We conclude that COX2-selective/preferential inhibitors thus should be prescribed with the same caution as nonselective NSAIDs during pregnancy and in the neonatal period.

Low endogenous glucocorticoid allows induction of kidney cortical cyclooxygenase-2 during postnatal rat development

In postnatal weeks 2-4, cyclooxygenase-2 (COX-2) is induced in the rat kidney cortex where it is critically involved in final stages of kidney development. We examined whether changes in circulating gluco- or mineralocorticosteroids or in their renal receptors regulate postnatal COX-2 induction. Plasma corticosterone concentration peaked at birth, decreased to low levels at days 3-13, and increased to adult levels from day 22. Aldosterone peaked at birth and then stabilized at adult levels. Gluco- and mineralocorticoid receptor (GR and MR) mRNAs were expressed stably in kidney before, during, and after COX-2 induction. 11 beta-hydroxysteroid dehydrogenase 2 was induced shortly after birth and was widely distributed in the whole collecting duct system in the suckling period and then returned to an adult pattern. Supplementation with corticosterone (20 mg.kg-1.day-1) or GR-specific dexamethasone (1 mg.kg-1.day-1) during low endogenous corticosterone suppressed renal COX-2 mRNA and protein and led to a restricted distribution of COX-2 immunolabeling. The ability of glucocorticoids to affect COX-2 was reflected in colocalization of GR-alpha and COX-2 immunoreactivity and mRNAs in thick ascending limb of Henle's loop. The MR antagonist potassium canrenoate (20 mg.kg-1.day-1) enhanced COX-2 expression from days 5 to 10, but low MR-specific concentrations of DOCA (1 mg.kg-1.day-1) had no effect on COX-2. Renomedullary interstitial cells expressed GR-alpha and COX-2. Dexamethasone suppressed COX-2 in these cells. Thus low plasma concentrations of corticosterone allowed for cortical and medullary COX-2 induction during postnatal kidney development. Increased circulating glucocorticoid in the postnatal period may damage late renal development through inhibition of COX-2.

Acute management of preterm labor

We are continually reminded that the preterm birth rate has failed to improve; in fact, it has increased over the last 20 years. Much of this increase is related to the tremendous strides made by neonatologists and the resulting increased willingness of obstetricians to deliver preterm babies from hostile intrauterine environments. However, there is still much to learn concerning the pathogenesis, accurate early detection, treatment, and prevention of spontaneous preterm labor. This article concentrates on the clinical diagnosis and acute management of this enigmatic clinical problem.

The adverse renal effects of prostaglandin-synthesis inhibitors in the newborn rabbit

Nonsteroidal anti-inflammatory drugs are frequently used during pregnancy (premature labor, polyhydramnios) and the immediate postnatal period (closure of patent ductus arteriosus). This article evaluates the renal effect of 3 nonspecific COX inhibitors (aspirin, indomethacin, and ibuprofen) in newborn rabbits. Five groups of anesthetized, ventilated, normoxemic 6-day-old rabbits (n = 52) were administered intravenous aspirin (40 mg/kg), indomethacin (2 mg/kg), and ibuprofen (0.02, 0.2, 2.0 mg/kg, respectively). Renal function and hemodynamics as assessed by inulin and para-aminohippuric acid clearances were measured before and in the hour after drug administration. In all groups of animals, the nonselective COX inhibitors induced an increase in renal vascular resistance and a consequent decrease in glomerular filtration rate and renal blood flow. Urine flow rate decreased significantly in all groups, except in the group receiving the lowest dose of ibuprofen. In newborn rabbits, aspirin, indomethacin, and ibuprofen induced intense renal vasoconstriction, which resulted in impaired renal function. This observation illustrates the major renal protective role played by the vasodilatory prostaglandins during the neonatal period, when the kidney is perfused at very low perfusion pressure. We conclude that all COX inhibitors should be administered with the same caution to the preterm neonate.

Placental restriction increases the expression of prostaglandin endoperoxide G/H synthase-2 and EP2 mRNA in the fetal sheep kidney during late gestation

There is evidence that fetal growth restriction is associated with impaired nephrogenesis and reduced numbers of mature nephrons at birth. It has been proposed that such impairment of renal growth may contribute to increased blood pressure in later life. Although prostaglandins (PG) play a key role in kidney development, it is unknown whether a poor fetal substrate supply alters the synthesis or actions of PG within the fetal kidney. Using real-time reverse transcriptase PCR, we have measured the effect of chronic placental restriction (PR) on the renal expression of PG endoperoxide G/H synthase-2 (PGHS-2), PGE(2) receptors EP(2) and EP(4), and renin mRNA in the sheep fetus in late gestation. Restriction of placental growth reduced fetal body weight (PR: 3.2 +/- 0.2 kg, control: 4.8 +/- 0.2 kg) and total kidney weight (PR: 19.7 +/- 1.8 g, control: 25.1 +/- 1.3 g). Mean fetal arterial PO(2) was reduced by PR (PR: 15.03 +/- 0.67 mm Hg, control: 21.3 +/- 0.87 mm Hg). Renal PGHS-2 mRNA was increased in the PR group (PR: 2.26 +/- 0.38, control: 1.20 +/- 0.31) and was inversely related to mean fetal arterial PO(2) in the PR and control groups [PGHS-2: -0.17 (PO(2)) + 4.69, r(2) = 0.26]. PR also increased renal EP(2) (PR: 1.57 + 0.24, control: 0.82 + 0.13) but not EP(4) mRNA. Renin mRNA was directly related to renal EP(2) [renin = 0.37 (EP(2)) + 0.97, r(2) = 0.29] and EP(4), [renin = 0.75 (EP(4)) + 0.44, r(2) = 0.38] mRNA expression. Thus, the restriction of placental growth and associated chronic hypoxemia appear to increase the renal capacity to synthesize and respond to PG, which may play an important role in maintaining renin mRNA expression in the growth-restricted fetus.

Pharmacology of cyclooxygenase-2 inhibition in the kidney

Cyclooxygenase (COX) exists as two unique isoforms (that is, COX-1 and COX-2) which are poorly understood with regard to their roles in renal function. The renal effects of conventional non-steroidal anti-inflammatory drugs (NSAIDs) are believed to result from the inhibition of one or both isoforms. Drugs that selectively inhibit COX-2 provide useful pharmacological tools for discerning the effects associated with the inhibition of the individual isoforms, and may help clarify the renal roles of COX-1 and COX-2. This review summarizes the current data on the renal expression of COX isoforms and their potential roles in renal function, and reviews the studies that have attempted to correlate renal functional changes with selective isoform inhibition. Since there are significant differences in the expression of COX isoforms in the kidneys of laboratory animals and humans, this review also examines the correlation of the results of COX inhibition in experimental studies in laboratory animals with clinical data. Because of potential interspecies differences in the roles of COX isoforms in renal function, animal models may have limited predictive value for patients, particularly those with renal risk factors. Accordingly, any uncertainty concerning the safety or therapeutic benefit of COX-2-specific drugs in these patient populations will need to be resolved with clinical investigations.

Renal tubular dysgenesis-like lesions and hypocalvaria. Report of two cases involving indomethacin

We describe a case of twins with twin-to-twin transfusion syndrome (TTS) who were found to have renal tubular dysgenesis (TRD)-like lesions and hypocalvaria attributed to indomethacin treatment of the mother for acute polyhydramnios. History of pregnancy, postnatal clinical course, pathological findings of the kidneys, and the skulls are presented and discussed. These findings include incompletely differentiated proximal tubules in the kidneys and hypoplastic calvaria in both twins. The renal tubular lesions were more marked in the donor than in the transfused twin, probably due to the greater degree of ischemia in that twin. This seems to be in favor of a vascular etiology of the renal defects. However, the fact that similar renal lesions and hypocalvaria were also present in the transfused twin seems to indicate that indomethacin played a role in their onset. This so-called kidney-skull connection has never been reported in conjunction with indomethacin therapy.

NSAID-induced nephrotoxicity from the fetus to the child

In this review we report data available from the literature on the use of nonsteroidal anti-inflammatory drugs (NSAIDs) and the development of nephrotoxicity in the fetus, neonates and children. Up to the present day, several cases of severe and sometimes irreversible renal insufficiency have been described in neonates exposed to indomethacin prenatally or in the first days of life for treatment of patent ductus arteriosus (PDA). Until now, very few studies have been carried out on alternative treatments for PDA in preterm infants; ibuprofen has been shown to be as effective as indomethacin in closing the ductus in this patient group without affecting renal function. In children, NSAID-induced renal failure is a rare event and is usually reversible after discontinuation of the drug. However, caution should be taken when NSAIDs are administered to individuals with preexisting renal problems or with other potentially nephrotoxic drugs. In these situations, new approaches such as cyclo-oxygenase-2 selective inhibitors or prostanoid receptor selective antagonists could lead to alternative therapies for use in paediatrics.

The renal hemodynamic effects of ibuprofen in the newborn rabbit

In early childhood, nonsteroidal anti-inflammatory drugs are mainly used to either prevent or treat premature labor of the mother and patent ductus arteriosus of the newborn infant. The most frequently used prostaglandin-synthesis inhibitor is indomethacin. Fetuses exposed to indomethacin in utero have been born with renal developmental defects, and in both the unborn child and the term and premature newborn this drug may compromise renal glomerular function. The latter has in the past also been observed when i.v. indomethacin or i.v. acetylsalicylic acid (aspirin) were administered to newborn rabbits. The present experiments were designed to evaluate whether ibuprofen has less renal side effects than indomethacin, as claimed. Three groups of anesthetized, ventilated, normoxemic neonatal rabbits were infused with increasing doses of ibuprofen (0.02, 0.2, 2.0 mg/kg body weight) and the following renal parameters were measured: urine volume, urinary sodium excretion, GFR, and renal plasma flow. Renal blood flow, filtration fraction, and the renal vascular resistance were calculated according to standard formulae. Intravenous ibuprofen caused a dose-dependent, significant reduction in urine volume, GFR, and renal blood flow with a fall in filtration fraction in the animals receiving the highest dose of ibuprofen (2 mg/kg body weight). There was a very steep rise in renal vascular resistance. Urinary sodium excretion decreased. These experiments in neonatal rabbits clearly show that acute i.v. doses of ibuprofen also have significant renal hemodynamic and functional side effects, not less than seen previously with indomethacin.

Controversies in tocolytic therapy

In general, tocolytic agents are effective in stopping uterine contractions and in temporarily delaying delivery. The benefit of stopping uterine contractions is dependent on the fetal status and gestational age. The rationale for stopping preterm labor is to improve neonatal outcome. At this time, the best way to improve neonatal outcome would be to assure delivery in a center capable of caring for a preterm infant and prescription of glucocorticoids to decrease the risk of respiratory distress syndrome and other neonatal complications. Intravenous tocolysis for premature labor has found a prominent place in the obstetrician's armamentarium. We recommend the use of magnesium sulfate as first-line therapy. When comparing maternal and fetal risks, side effects, and the safety profile, magnesium sulfate is superior to beta-mimetics; however, there are still significant problems with potential morbidity and mortality for both mother and fetus with any tocolytics. Adjunctive use of indomethacin with magnesium sulfate may be used through 32 weeks for up to 48 hours at a time. Most tocolytics are effective in stopping labor for 48-72 hours. None have been shown to decrease the rate of preterm delivery. Once the uterus is quiescent and intravenous tocolytics are stopped, prolonged use of tocolytics has not been shown to be effective in preventing preterm birth. Tocolytics have significant long-term side effects to the mother's cardiovascular system, carbohydrate metabolism, and the fetal cardiovascular system. Thus, the prolonged use of prophylactic tocolytics after cessation of intravenous medications is not recommended. Tocolytics may be an appropriate therapy during preterm labor vaginal bleeding, ruptured membranes, multiple gestation, or advanced cervical dilatation. In all situations, however, careful guidelines must be observed. These guidelines include: (1) maternal and fetal well-being must be established before tocolytic therapy; (2) causes of preterm labor should be evaluated and treated when possible; (3) the risk/benefit ratio for both the mother and fetus must be re-evaluated on an ongoing basis; (4) when tocolytics are given before pulmonary maturity, then antenatal corticosteroids also should be considered in every case; (5) long-term use of tocolytics is difficult to justify at this time; (6) the safest tocolytic should be used for the shortest amount of time possible. It is doubtful, because of the nature of tocolytics, that newer tocolytics will be developed that will eliminate the problems of preterm delivery. Preterm delivery is an end-stage symptom of a multifactorial disease. Preterm labor is one of the last symptoms in a cascade of biochemical events that lead to preterm delivery. The most appropriate way to end preterm delivery would be to prevent the causes that initiate the cascade that ends in preterm labor. Authors' Note: Literally hundreds of papers have been written in the last 30 years on tocoloysis. For the purposes of space, when studies are summarized in peer-reviewed articles, we have referenced the reviews instead of the individual studies.

Renal tubular dysgenesis in twin-twin transfusion syndrome

In twin-twin transfusion syndrome (TTTS), the disparity in circulation is reflected in discordant fetal growth, urine output, and amniotic fluid accumulation. The effect of uneven shunting of the growth factor and nutrient-rich vasculature on development and differentiation of the kidney has not been well studied. We analyzed renal tubular growth and differentiation in 25 fetal autopsies with TTTS (13 donors and 12 recipients, including 9 sibling pairs) between 18 and 33 weeks gestation. Immunohistochemical markers for fumarylacetoacetate hydrolase (FAH), Leu-M1, and Lotus tetragonolobus (LTA) were used to identify proximal convoluted tubules, and epithelial membrane antigen (EMA) was used to demonstrate distal convoluted and collecting tubules. FAH appeared to be more specific and reliable than either Leu-M1 or LTA in the identification of proximal tubules. Donors tended to demonstrate a paucity of proximal tubules with crowding of glomeruli characteristic of renal tubular dysgenesis (RTD). The degree of dysgenesis was greater in later gestations and associated with more severe growth restriction. Donors in TTTS are at risk for the development of RTD. Several authors suggest ischemia as the underlying cause of "acquired" RTD. However, in this setting there is no evidence of cell death or necrosis, and we suggest that hypoperfusion leading to decreased glomerular filtration is the underlying etiology, with the severity of RTD related to the degree of shunting.

Assessing the teratogenic potential of angiotensin-converting enzyme inhibitors in pregnancy

To assess the teratogenic potential of angiotensin-converting enzyme (ACE) inhibitors, we report on 20 prospective pregnancies and 85 identified from articles in the literature. The anomaly rate was 20.6% in small series <10 entrants (95% CI 8.7-37.9%) and 1.4% in larger series > or =10 entrants (95% CI 0.03-7.3%) p=0.0016. The most consistent anomaly seen, skull hypoplasia, along with renal dysfunction appear to be more related to prolonged or late pregnancy exposure than to first trimester exposure. There is little supportive evidence that ACE inhibitors (captopril or enalapril) are teratogenic. There seems to be no absolute reason to discontinue these 2 medications prior to pregnancy, nor to create anxiety when a patient is identified with the combination of early pregnancy and treatment with these medications. There appears to be reason to discontinue the medication in pregnancy but the adverse event rate cannot be assessed because of inadequate prospective information.