Strain differences in response of Sprague-Dawley and Long Evans Hooded rats to the teratogen nitrofen

Repeat dose and reproductive toxicity of thrombopoietin mimic peptide in Sprague-Dawley rats

Thrombopoietin mimic peptide (TMP) is a novel thrombopoietin receptor agonist. In this report, we evaluated the potential toxicity of TMP in repeat-dose toxicity and reproductive/developmental toxicity studies (segment Ⅰ, Ⅱ, Ⅲ). TMP was administered subcutaneously to Sprague-Dawley (SD) rats at 5, 15 or 50 mcg/kg. In repeat-dose toxicity study, the rats were administrated three times a week for 26 week with a 4-week recovery. TMP could produce anti-drug antibodies and induce platelet counts increase, megakaryocyte proliferation. While platelet counts decreased gradually and returned to normal after 4 weeks in male rats. Other significant findings included myelofibrosis of bone marrow, hepatic extramedullary hematopoiesis, splenic lymphocytic depletion and bone hyperostosis. All treatment-related effects were reversed following recovery. The NOAEL of repeat-dose toxicity in female rats is 5 mcg/kg. In the reproductive/developmental toxicity (segment Ⅰ, Ⅲ), no deaths occurred, and no general toxicological effects or abnormal reproductive functions were observed. In embryo-fetal developmental toxicity study (segment Ⅱ), the number of resorbed fetuses in the 50 mcg/kg group was significantly increased. The NOAEL as related to reproductive/developmental toxicity in these rats was 15 mcg/kg.

Beyond the diaphragm and the lung: a multisystem approach to understanding congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a birth defect characterized by the incomplete closure of the diaphragm and herniation of abdominal organs into the chest during gestation. This invariably leads to an impairment in fetal lung development (pulmonary hypoplasia) that involves the pulmonary vessels (vascular remodeling) leading to postnatal pulmonary hypertension. Moreover, approximately 60% of CDH survivors have long-term comorbidities, including critical cardiac anomalies, neurodevelopmental impairment, gastroesophageal reflux, and musculoskeletal malformations. While the pathophysiology of the diaphragmatic defect and pulmonary hypoplasia have been studied in detail over the decades, less is known about the other organs affected in CDH. In this review, we searched the literature for reports on other organs beyond the lung and diaphragm in human and experimental models of CDH. We found studies reporting gross morphometric changes and alterations to biological pathways in the heart, brain, liver, kidney, gastrointestinal tract, and musculoskeletal system. Given the paucity of literature and the importance that these comorbidities play in the life of patients with CDH, further studies are needed to comprehensively uncover the pathophysiology of the changes observed in these other organs.

Fluoride exposure and hypothyroidism in a Canadian pregnancy cohort

BACKGROUND

While fluoride can have thyroid-disrupting effects, associations between low-level fluoride exposure and thyroid conditions remain unclear, especially during pregnancy when insufficient thyroid hormones can adversely impact offspring development.

OBJECTIVES

We evaluated associations between fluoride exposure and hypothyroidism in a Canadian pregnancy cohort.

METHODS

We measured fluoride concentrations in drinking water and three dilution-corrected urine samples and estimated fluoride intake based on self-reported beverage consumption. We classified women enrolled in the Maternal-Infant Research on Environmental Chemicals Study as euthyroid (n = 1301), subclinical hypothyroid (n = 100) or primary hypothyroid (n = 107) based on their thyroid hormone levels in trimester one. We used multinomial logistic regression to estimate the association between fluoride exposure and classification of either subclinical or primary hypothyroidism and considered maternal thyroid peroxidase antibody (TPOAb) status, a marker of autoimmune hypothyroidism, as an effect modifier. In a subsample of 466 mother-child pairs, we used linear regression to explore the association between maternal hypothyroidism and child Full-Scale IQ (FSIQ) at ages 3-to-4 years and tested for effect modification by child sex.

RESULTS

A 0.5 mg/L increase in drinking water fluoride concentration was associated with a 1.65 (95 % confidence interval [CI]: 1.04, 2.60) increased odds of primary hypothyroidism. In contrast, we did not find a significant association between urinary fluoride (adjusted odds ratio [aOR]: 1.00; 95%CI: 0.73, 1.39) or fluoride intake (aOR: 1.25; 95%CI: 0.99, 1.57) and hypothyroidism. Among women with normal TPOAb levels, the risk of primary hypothyroidism increased with both increasing water fluoride and fluoride intake (aOR water fluoride concentration: 2.85; 95%CI: 1.25, 6.50; aOR fluoride intake: 1.75; 95%CI: 1.27, 2.41). Children born to women with primary hypothyroidism had lower FSIQ scores compared to children of euthyroid women, especially among boys (B coefficient: -8.42; 95 % CI: -15.33, -1.50).

DISCUSSION

Fluoride in drinking water was associated with increased risk of hypothyroidism in pregnant women. Thyroid disruption may contribute to developmental neurotoxicity of fluoride.

Developmental and reproduction toxicity studies of Biolimus A9 in SD rats

Biolimus A9 (BA9) is a novel rapamycin derivative. In this report we evaluated the potential toxicity of BA9 in a developmental and reproduction toxicity study (segment Ⅰ, Ⅱ, Ⅲ). In segment I, body weight gains in F0 rats receiving 0.80 mg/kg/day were decreased. A lower fertility index of males was observed and females failed to become pregnant in the 0.80 mg/kg/day group. The number of live fetuses and implantations were decreased while the number of dead fetuses, resorptions, and implantation losses were increased in the 0.12 mg/kg/day group. In segment Ⅱ, maternal toxicity: body weight gains in F0 females receiving 0.036 and 0.090 mg/kg/day group were decreased. Embryo toxicity: In the 0.090 mg/kg/day group, weights and body lengths of fetuses were decreased, the numbers of viable fetuses was decreased and resorbed fetuses increased. Teratogenic effects: The percent of visceral variations and skeletal variations were both increased in the 0.090 mg/kg/day group. In segment Ⅲ, dosing F0 rats with BA9 at dose levels of 0.12 and 0.80 mg/kg/day resulted in reproductive and maternal toxicity, consisting of prolonged labor, dystocia, increased mortality, along with reductions in lactation food consumption. F1 rats in the 0.12 mg/kg/day group showed reproductive and developmental toxicity consisting of body weight decreases, decreased food consumption after weaning and a reduction in the gestation index of pregnant rats. Based on these findings, the no-observed-adverse-effect-level (NOAEL) of BA9 toxicity in segment Ⅰ and Ⅲ was 0.02 mg/kg/day. The NOAEL in segment Ⅱ was 0.015 mg/kg/day.

Congenital diaphragmatic hernia: current management strategies from antenatal diagnosis to long-term follow-up

Congenital diaphragmatic hernia (CDH) is a developmental birth defect consisting of a diaphragmatic defect and abnormal lung development. CDH complicates 2.3-2.8 per 10,000 live births. Despite efforts to standardize clinical practice, management of CDH remains challenging. Frequent re-evaluation of clinical practices in CDH reveals that management of CDH is evolving from one of postnatal stabilization to prenatal optimization. Translational research reveals promising avenues for in utero therapeutic intervention, including fetoscopic endoluminal tracheal occlusion. These remain highly experimental and demand improved antenatal diagnostics. Timely diagnosis of CDH and identification of severely affected fetuses allow time for delivery planning or in utero therapeutics. Optimal perinatal care and surgical treatment strategies are highly debated. Improved CDH mortality rates have placed increased emphasis on identifying and monitoring the long-term sequelae of disease throughout childhood and into adulthood. We review the current management strategies for CDH, highlighting where progress has been made, and where future developments have the potential to revolutionize care in this vulnerable patient population.

Reproductive and developmental toxicity study of caffeic acid in mice

Caffeic acid is an antioxidant commonly used to promote hematopoiesis and hemostasis. However, little is known about its systemic safety profile in reproduction and development. Here, we focused on the reproductive and developmental toxicity of caffeic acid in F0 female mice and F1 offspring. In the three-segment study, the F0 female mice were continuously exposed to 0, 0.15, 5 or 150 mg/kg/day of caffeic acid by gavage. We found that 5 mg/kg/day and 150 mg/kg/day of caffeic acid affected implantation of embryos when administered before gestation day 6. In addition, 150 mg/kg/day of caffeic acid affected fetal weight gain. No maternal toxicity, fetal teratogenesis or post-natal effects on pup development were observed. The no-observed-adverse-effect-level was 0.15 mg/kg/day for pregnant mice under the conditions of this study.

Role of Risk of Bias in Systematic Review for Chemical Risk Assessment: A Case Study in Understanding the Relationship Between Congenital Heart Defects and Exposures to Trichloroethylene

The National Academy of Science has recommended that a risk of bias (RoB; credibility of the link between exposure and outcome) assessment be conducted on studies that are used as primary data sources for hazard identification and dose-response assessment. Few applications of such have been conducted. Using trichloroethylene and congenital heart defects (CHDs) as a case study, we explore the role of RoB in chemical risk assessment using the National Toxicology Program's Office of Health Assessment and Translation RoB tool. Selected questions were tailored to evaluation of CHD and then applied to 12 experimental animal studies and 9 epidemiological studies. Results demonstrated that the inconsistent findings of a single animal study were likely explained by the limitations in study design assessed via RoB (eg, lack of concurrent controls, unvalidated method for assessing outcome, unreliable statistical methods, etc). Such limitations considered in the context of the body of evidence render the study not sufficiently reliable for the development of toxicity reference values. The case study highlights the utility of RoB as part of a robust risk assessment process and specifically demonstrates the role RoB can play in objectively selecting candidate data sets to develop toxicity values.

Medical interventions to reverse pulmonary hypoplasia in the animal model of congenital diaphragmatic hernia: A systematic review

We aimed to systematically review all published pre-clinical research on prenatal medical treatment of pulmonary hypoplasia in congenital diaphragmatic hernia (CDH). Background The neonatal mortality due to isolated CDH remains high. Whether fetal endoscopic tracheal occlusion (FETO) reduces mortality is still to be demonstrated. Therefore more potent preferentially medical therapy would be welcomed. Methods We searched MEDLINE (Pubmed), Embase and the Web of Science including all studies from the earliest date (1951) to December 2013. Article quality was assessed using the modified CAMRADES checklist. Inclusion criteria were those animal studies addressing prenatal medical interventions and principal variables were confirmation of a diaphragmatic defect, lung to body weight ratio (LBWR), formal airway morphometry or DNA/protein content. Results In total 983 articles were identified. Following abstract review, 96 articles were assessed by two authors in agreement with a third for eligibility. Of these, 43 were included in the final analysis. The median number of study quality checklist items (maximum 10) scored was 4 (IQ range: 2-5). Thirty (69.8%) of studies were in the nitrofen rat. The majority were treated with vitamins or glucocorticoids. Single studies reported some improvement in lung morphology with alternative therapies. It was impossible to identify a pattern in animal model selection or creation, mode, time point or duration of treatment and readouts. Only one study reported a sample size calculation. Conclusion Comparison in pre-clinical studies in CDH is challenging due to methodological variation. Agreed standardized methods need to be applied in future investigation of new medical therapies.

Final Report of the Safety Assessment of Cosmetic Ingredients Derived From Zea Mays (Corn)

Many cosmetic ingredients are derived from Zea mays (corn). While safety test data were not available for most ingredients, similarities in preparation and the resulting similar composition allowed extrapolation of safety data to all listed ingredients. Animal studies included acute toxicity, ocular and dermal irritation studies, and dermal sensitization studies. Clinical studies included dermal irritation and sensitization. Case reports were available for the starch as used as a donning agent in medical gloves. Studies of many other endpoints, including reproductive and developmental toxicity, use corn oil as a vehicle control with no reported adverse effects at levels used in cosmetics. While industry should continue limiting ingredient impurities such as pesticide residues before blending into a cosmetic formulation, the CIR Expert Panel determined that corn-derived ingredients are safe for use in cosmetics in the practices of use and concentration described in the assessment.

Evaluation of developmental toxicant identification using gene expression profiling in embryonic stem cell differentiation cultures

The murine embryonic stem cell test (EST) is an alternative testing method designed to assess potential developmental toxicity of compounds. The implementation of transcriptomics in the EST has been shown to reduce the culture duration and improve endpoint evaluation and is expected to result in an enhanced predictability and definition of the applicability domain. We evaluated the identification of developmental toxicity in the EST using two gene sets ("Van_Dartel_heartdiff_24h" and "EST biomarker genes") defined in our earlier studies. Nonexposed embryonic stem cells (ESC) differentiation cultures were sampled 0, 24, and 48 h after initiation of differentiation. Additionally, cultures exposed to 12 diverse well-characterized positive and negative developmental toxicants were isolated 24 h after the onset of exposure. Inhibition of ESC differentiation was evaluated in parallel by morphological scoring on culture day 10. Transcriptomics analysis was conducted using the Affymetrix Gene Chips platform. We applied principal component analysis on the basis of the two predefined gene sets to define the "differentiation track" that represents ESC differentiation. The significance of derivations in the gene expression-based differentiation track because of compound exposures were evaluated to determine developmental toxicity of tested compounds. We successfully predicted developmental toxicity using transcriptomics for 83% (10/12) and 67% (8/12) of the compounds, respectively, using the two predefined gene sets ("Van_Dartel_heartdiff_24h" and "EST biomarker genes"). Our study suggests that the application of transcriptomics may improve the applicability of the EST for the prediction of the developmental toxicity of chemicals.

Vitamin A deficiency (VAD), teratogenic, and surgical models of congenital diaphragmatic hernia (CDH)

Congenital diaphragmatic hernia (CDH) is a congenital malformation that occurs with a frequency of 0.08 to 0.45 per 1,000 births. Children with CDH are born with the abdominal contents herniated through the diaphragm and exhibit an associated pulmonary hypoplasia which is frequently accompanied by severe morbidity and mortality. Although the etiology of CDH is largely unknown, considerable progress has been made in understanding its molecular mechanisms through the usage of genetic, teratogenic, and surgical models. The following review focuses on the teratogenic and surgical models of CDH and the possible molecular mechanisms of nitrofen (a diphenyl ether, formerly used as an herbicide) in both induction of CDH and pulmonary hypoplasia. In addition, the mechanisms of other compounds including several anti-inflammatory agents that have been linked to CDH will be discussed. Furthermore, this review will also explore the importance of vitamin A in lung and diaphragm development and the possible mechanisms of teratogen interference in vitamin A homeostasis. Continued exploration of these models will bring forth a clearer understanding of CDH and its molecular underpinnings, which will ultimately facilitate development of therapeutic strategies.

Kidney development in the nitrofen-induced pulmonary hypoplasia and congenital diaphragmatic hernia in rats

BACKGROUND/PURPOSE

The relationship of the developing lung and kidney is not completely understood. Renal enlargement has been reported in association with pulmonary hypoplasia in congenital diaphragmatic hernia (CDH). Recent studies suggest that retinoids may be involved in the pathogenesis of CDH. The aims of this study were to investigate the effects of pulmonary hypoplasia on renal development and to evaluate retinoids status of kidneys in the nitrofen model of CDH.

METHODS

Pregnant rats were exposed to either olive oil or 100 mg of nitrofen on day 9.5 of gestation. Fetuses were recovered at term and divided into 3 groups: 1, control (n = 69); 2, nitrofen without CDH (n = 25); and 3, nitrofen with CDH (n = 40). Kidneys were dissected, weighed, and processed for biochemical measurements of DNA, proteins, total retinol content, and for immunohistochemical staining of proliferating cells.

RESULTS

Kidneys were smaller in nitrofen-exposed animals vs control animals (group 3, 0.65 +/- 0.08; group 2, 0.62 +/- 0.09 vs group 1, 0.73 +/- 0.09% of body weight, P < .001), and there were no differences between right and left kidney weight in all the 3 groups. Regression of total kidney weight on body weight showed a linear direct correlation between them in all the groups. Total amount of DNA was significantly reduced in nitrofen-exposed animals vs controls (group 3, 80.58 +/- 35.65; group 2, 64.71 +/- 20.28 vs group 1, 110.34 +/- 42.15 microg, P < .01), but the DNA concentration remained the same in the 3 groups (group 3, 3.59 +/- 1.26; group 2, 3.06 +/- 1.19; group 1, 3.43 +/- 1.05 microg DNA/mg kidney). Total protein content (group 3, 1145.59 +/- 500.36; group 2, 993.2 +/- 276.62; group 1, 1287.48 +/- 312.52 microg), protein concentration (group 3, 49.76 +/- 11.12; group 2, 43.95 +/- 6.79; group 1, 47.38 +/- 6.93 microg protein/mg kidney), and protein-to-DNA ratio (group 3, 15.12 +/- 5.98; group 2, 16.22 +/- 6.85; group I, 16.16 +/- 7.02 microg/microg) were similar in all groups. Retinol concentration was significantly reduced in both nitrofen-exposed groups compared with the control group (group 3, 1.35 +/- 0.24; group 2, 1.28 +/- 0.11; group 1, 2.53+/-0.61 microg retinol/g kidney). Proliferation index was similar in all 3 groups (group 3, 50.43 +/- 8.81; group 2, 47.96 +/- 6.01; group 1, 47.64 +/- 5.76% of proliferating cells).

CONCLUSIONS

Our data clearly show that renal enlargement in association with pulmonary hypoplasia is not seen in the nitrofen-induced CDH. These results rule out any possible relationship between lung and kidney development. Moreover, kidneys are hypoplastic in both nitrofen-exposed groups and have reduced retinol content, suggesting that a retinoid pathway disruption could be the common mechanism in the pathogenesis of lung and kidney hypoplasia in the nitrofen model of CDH.

Fetal heart development in the nitrofen-induced CDH rat model: the role of mechanical and nonmechanical factors

BACKGROUND/PURPOSE

In congenital diaphragmatic hernia (CDH), it was recently shown that early and late gestational lung underdevelopment is caused by nonmechanical and mechanical factors, respectively. Heart underdevelopment, which might predict lung hypoplasia, is commonly attributed to mechanical factors. The authors analyzed whether nonmechanical and mechanical factors affect cardiac growth and correlations between lung and heart weights during gestation.

METHODS

Left-sided CDH was induced in pregnant Wistar rats by administration of nitrofen on E9.5. At selected gestational ages (E18, E20, and E22), the lungs and heart were harvested, weighed, and analyzed for DNA and protein contents. Left lung and heart weights were correlated at those gestational ages. Two experimental groups: nitrofen without CDH (nitrofen), and nitrofen with CDH (CDH), were compared with normal controls.

RESULTS

At E18, both nitrofen-exposed groups presented similar and significant left lung (LL) hypoplasia. As gestation progressed (E20 and E22), in the nitrofen group left lung (LL) hypoplasia decreased, whereas in the CDH group LL hypoplasia was exacerbated relative to normal controls. In contrast, at E18 and E20, heart-to-body weight ratios as well as cardiac DNA and protein contents were reduced significantly in all animals exposed to nitrofen, with no significant differences observed between nitrofen and CDH groups. As gestation progressed, the difference between cardiac parameters in nitrofen-exposed and normal control rats diminished, and at E22 no significant differences were documented. In the CDH group, significant correlations were seen between lung and heart weights at E18 (r = 0.65; P <.05) and E20 (r = 0.4; P <.05), whereas at term gestation (E22) no significant correlation was observed (r = 0.21, not significant).

CONCLUSIONS

Nonmechanical factors, which might be directed by nitrofen, play a role in the pathogenesis of lung and heart hypoplasia manifested precociously in fetal life, whereas mechanical compression might influence only lung growth during late gestation. Heart weight predicts lung weight only in early gestational ages.

Congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a lethal human birth defect. Hypoplastic lung development is the leading contributor to its 30-50% mortality rate. Efforts to improve survival have focused on fetal surgery, advances in intensive care and elective delivery at specialist centres following in utero diagnosis. The impact of abnormal lung development on affected infants has stimulated research into the developmental biology of CDH. Traditionally lung hypoplasia has been viewed as a secondary consequence of in utero compression of the fetal lung. Experimental evidence is emerging for a primary defect in lung development in CDH. Culture systems are providing research tools for the study of lung hypoplasia and the investigation of the role of growth factors and signalling pathways. Similarities between the lungs of premature newborns and infants with CDH may indicate a role for antenatal corticosteroids. Further advances in postnatal therapy including permissive hypercapnia and liquid ventilation hold promise. Improvements in our basic scientific understanding of lung development may hold the key to future developments in CDH care.

Pulmonary hypoplasia induced by liquid paraffin injection into fetal thoracic cavity with special reference to renal development in rats

The present study was designed to clarify lung-kidney interrelation in fetal rats. On fetal day 20, liquid paraffin (LP) was injected into fetal thoracic cavity to produce pulmonary hypoplasia. No significant difference in body and renal weights were noted between the LP injected and control fetuses. The weight of lung, however, was significantly lower in the LP injected fetuses than in the control ones. Histological examinations on the lung and kidney of the LP injected fetuses revealed that the lung was hypoplastic characterized by rich interstitium and reduced air spaces. In the kidney, mature types of glomeruli and profiles of proximal tubules near them were increased in number. Furthermore, strong expression of EGF immunoreactivity was noted in the apical cytoplasm of epithelium of the proximal tubules in the LP injected fetuses. These findings indicate that lung-kidney interrelation exists in fetal rats during late gestational days, and suggest that interruption of the lung development induces accelerated growth of the kidney in fetal rats.

Experimental ureterohydronephrosis in fetal rats

This study tests the hypothesis that prenatal exposure to 2,4-dichlorophenyl-p-nitrophenyl ether (nitrofen), an herbicide known to induce pulmonary hypoplasia and other malformations in fetal rats, also may induce ureterohydronephrosis (UHN) and oligohydramnios. Time-dated pregnant Wistar rats were given 100 mg of the chemical on day 9 or 11 of gestation, and the findings in their fetuses were compared with those of suitable controls. Marked bilateral UHN was found in the majority of exposed fetuses, but without evidence of either mechanical obstruction or dysplastic parenchymal lesions. These animals had various degrees of lung hypoplasia. The amount of fluid in their amniotic sacs was increased rather than decreased and it was independent of lung weight but correlated to some extent with UHN grade. Urinary tract dilatation and polyhydramnios in this model most likely are attributable to polyuria caused by nitrofen-induced impairment of renal concentrating capacity. This relatively simple animal model might facilitate research into some aspects of the physiology of nonobstructive, prenatally dilated urinary tracts.

Testicular maldescent and maldevelopment in fetal rats prenatally exposed to nitrofen

In the rat model of nitrofen-induced congenital diaphragmatic hernia, we found the testicles in a high abdominal position in many male animals, and undertook to investigate whether the teratogen interferes with testicular descent and development. Male fetuses from time-mated Wistar rats treated intragastrically with 100 mg nitrofen dissolved in oil on day 9.5 of gestation were compared with control fetuses from mothers receiving only vehicle. The litters were recovered by cesarean section on days 17, 19, and 21 of gestation; the position of the testicles in male animals was recorded, and their volume was measured prior to histological assessment of mean tubular diameter, number of germ cells per tubule, and degree of collagenization of the tunica albuginea. Testicular maldescent was present in 100% of nitrofen-exposed fetuses on the 17th gestational day, 77% of those recovered on day 19, and 41% of those near term (21st day), whereas all control animals but 1 had "descended" gonads on all three days. Testicular volume was significantly decreased in treated fetuses on the 21st gestational day, and the mean tubular diameter was significantly decreased in all three age groups. Experimental and control animals had similar numbers of germ cells per tubule. The albuginea layer had apparently normal collagen content in all groups. These findings suggest that prenatal exposure to nitrofen interferes with both transabdominal descent of the testicle (transinguinal descent is postnatal in the rodent) and its normal development. Previous evidence and the present results authorize speculation on the possible role of nitrofen-induced prenatal thyroid hypofunction in the pathogenesis of maldescent and maldevelopment in this model, since thyroid hormones act directly on Sertoli cells, which secrete müllerian inhibiting substance, which is likely responsible for transabdominal descent.

The kidney in the fetal rat model of congenital diaphragmatic hernia induced by nitrofen

This paper explores whether there is a correlation between kidney and lung growths in an experimental model of congenital diaphragmatic hernia (CDH) induced by intragastric administration of Nitrofen (115 mg/kg) in olive oil on time-dated pregnant Wistar rats at the 9th day of gestation. For comparison we used pregnant rats treated with olive oil alone. Twenty-nine normal fetuses from 3 control rats and 24 left CDH fetuses from 6 Nitrofen rats were studied. Fetal (3.6 +/- 0.8 v 4.9 +/- 0.4 g, P < .001) and total lung (2% +/- 0.5% v 2.6% +/- 0.3% of body weight, P < .001) weights were significantly decreased in animals with CDH. Kidneys were also smaller in CDH animals although not significantly (0.7% +/- 0.1% v 0.8% +/- 0.1% of body weight, P = .05) and were also histologically immature. Regression of kidney weight on body weight for both groups yielded regression lines that were identical at analysis of covariance and all data points from the CDH group were within the control group 95% confidence limits. After converting raw data into lung/body and kidney/body weight ratios, no inverse correlation suggesting a feedback mechanism of growth regulation between both organs could be found. Since nitrofen acts through modifications of the thyroid hormone status in both dam and fetus, altered maturation of several organs should be expected although some of them, like the lung, are the leading targets. The present CDH rodent model is probably different from the human malformation in spite of the striking anatomic similarities between them.(ABSTRACT TRUNCATED AT 250 WORDS)

The significance of the dilated renal pelvis in the nitrofen-exposed rat fetus: effects on morphology and function

Previously (R. J. Kavlock, B. F. Rehnberg, and E. H. Rogers, 1987, Teratology 36, 51-58) we reported that gestational exposure of rats to adriamycin induced alterations in development of the fetal renal papilla that persisted postnatally. The morphological effect was associated with functional deficits in neonatal animals as seen by their performance during a test of renal concentrating ability in the second postnatal week. In the present study, we utilized an experimental approach similar to that in the adriamycin study to evaluate the fate of the dilated renal pelvis that is induced in fetal rats following prenatal exposure to nitrofen. Groups of Long-Evans rats were exposed to 0, 6.25, 12.5, or 25 mg/kg of nitrofen on gestation Days 7-16. Renal morphology of the offspring were determined on gestation Day 21 and postnatal Week 5. The postnatal cohort was tested in the second postnatal week for their ability to excrete an osmotically concentrated urine. As was the case with adriamycin, the renal concentrating ability in the neonate was reduced and poor performance in the function test was associated with permanence of the morphological effect. By utilizing a standardized semiquantitative procedure to describe the status of the kidneys and ureters during development in combination with physiological assessment of organ performance, we were able to assess the morphological and functional development of the kidney. In the absence of other anomalies we suggest that offspring be monitored during postnatal development when alterations of the fetal renal papilla are observed in standard teratology bioassays in order to determine whether the effect is transient or permanent.