Perinatal nephropathies

Postnatal fate of prenatal-induced fetal alterations in laboratory animals

Currently it is common practice to evaluate the developmental toxicity hazard of chemicals or pharmaceuticals by evaluation of fetuses after administration of the compound to pregnant animals. These studies are designed to provide possible compound-related fetal changes near term, which are usually classified into malformations or variations. Malformations, but not variations are expected to adversely affect the survival or health. Therefore, classification has striking different regulatory consequences. For categorization as variation reversibility is an important criterion, but it is usually not examined in a standard guideline study. Although this issue has already been recognized long time ago, data dealing with the postnatal reversibility of fetal alterations are still rare. In the current review, literature data, regulatory documents as well as in-house data were compiled. Beside skeletal alterations of skull, vertebral column, ribs, shoulder and pelvic girdle, and extremities, kidney and heart defects are discussed and assessed.

TCDD-induced cyclooxygenase-2 expression is mediated by the nongenomic pathway in mouse MMDD1 macula densa cells and kidneys

Cyclooxygenase-2 (Cox-2) plays a critical role in TCDD-induced hydronephrosis in mouse neonates. In this study we found that induction of Cox-2 by TCDD in MMDD1, a mouse macula densa cell line, is accompanied with a rapid increase in the enzymatic activity of cytosolic phospholipase A2 (cPLA2) as well as activation of protein kinases. Calcium serves as a trigger for such an action of TCDD in this cell line. These observations indicate that the basic mode of action of TCDD to induce the rapid inflammatory response in MMDD1 is remarkably similar to those mediated by the nongenomic pathway of aryl hydrocarbon receptor (AhR) found in other types of cells. Such an action of TCDD to induce Cox-2 in MMDD1 was not affected by "DRE decoy oligonucleotides" treatment or by introduction of a mutation on the DRE site of Cox-2 promoter, suggesting that this route of action of TCDD is clearly different from that mediated by the classical genomic pathway. An in vivo study with Ahr(nls) mouse model has shown that TCDD-induces Cox-2 and renin expression in the kidneys of the Ahr(nls) mice as well as Ahr(+/-) mice, but not in the Ahr(-/-) mice, indicating that this initial action of TCDD in mouse kidney does not require the translocation of AhR into the nucleus, supporting our conclusion that induction of Cox-2 by TCDD in mouse kidney is largely mediated by the nongenomic pathway of TCDD-activated AhR.

Evaluation of the persistence of hydronephrosis induced in mice following in utero and/or lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is an extremely potent teratogen in mice, inducing structural malformations in the kidney and secondary palate. Maternal depots of TCDD, stored primarily in adipose tissue, are mobilized during the nursing period. Thus, lactation serves as a significant route of exposure for the developing neonate. The objective of this present investigation was to assess whether hydronephrosis persisted postnatally, as well as to determine if the renal lesion could be induced lactationally. Pregnant C57BL/6N mice were treated once by gavage with 0, 3, or 12 micrograms TCDD/kg body wt on Gestation Day (GD) 6. All dams were allowed to litter, and each litter was standardized at random to a size of six pups. Standardized litters were then reciprocally cross-fostered on the day of birth. Postnatal Day (PND) 0, resulting in the establishment of four experimental groups: pups not exposed by either route, pups exposed only in utero, pups exposed only lactationally, and pups exposed by both routes. Pups were euthanized at one of two time points, either at weaning (PND 25) or at puberty (PND 67). TCDD was not overtly toxic to the dams or neonates with the dosing regime used in this study. Hydronephrotic incidence and severity, while greatest for pups receiving dual exposure, were essentially the same for pups exposed in utero only vs lactationally only. Lactational exposure induced hydronephrosis (HN), as well as exacerbated the severity of existing HN which was induced in utero. Regardless of the exposure group, the severity of the renal lesion was always greater in the right kidney than in the left. There were no sex-related differences in either the incidence or the severity of HN, nor was there any difference in response between PNDs 25 and 67. These data suggest that the renal lesion persists from weaning through puberty, despite the cessation of exposure. However, the data indicate that partial recovery from HN induced in utero occurs during the early postnatal period, as both hydronephrotic incidence and severity decreased with increasing age between GD 18 and PND 25. Recovery was most pronounced in the left kidney regardless of dose, thus suggesting that the ability to recover may in part be dependent upon the extent of renal damage.

Fate of adriamycin-induced dilated renal pelvis in the fetal rat: functional and morphological effects in the offspring

Previously we reported that gestational exposure to Adriamycin, an anthracycline antibiotic used in the treatment of neoplasms, reduced renal function in the neonatal rat, and we suggested that alterations in the development of the renal papilla might be responsible for the dysfunction. In this study we exposed groups of Sprague-Dawley rats to 0, 1.0, 1.25, or 1.5 mg/kg of Adriamycin on gestation days 10-12, a period previously shown to be effective in altering postnatal renal function with this compound. Offspring were evaluated at several developmental periods in order to 1) precisely define the morphological status of the urogenital system in Adriamycin-treated offspring; 2) replicate the finding of a decreased renal concentrating ability in the neonates; 3) determine the transience/permanence of any morphological effect; and 4) correlate any permanent alterations in urogenital morphology with our indicator of neonatal functional competence. Maternal Adriamycin treatment induced alterations in the development of the renal papilla that persisted well into the postnatal life of the offspring. The first appearance of the morphological alteration occurred in the absence of other general indicators of developmental toxicity such as growth retardation. The determination of the ultimate fate and functional consequences of the structural alterations required postnatal evaluations of the renal system. Finally, a relatively simple test of renal function in the neonate proved to be predictive of the permanence of the morphological effect, and the absolute test result showed a strong correlation with the incidence of the morphological effect in the overall population.

TCDD alters the extracellular matrix and basal lamina of the fetal mouse kidney

The teratogenic effects of the dioxin 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) have previously been studied in several species, and hydronephrosis has been reported to be a frequent abnormality in near-term fetuses. C57BL/6N female mice, given 12 micrograms/kg TCDD, P.O., on day 10 of gestation were killed on days 14, 15, and 16; fetal kidneys were collected and prepared for either immunofluorescent localization of several extracellular matrix components (ECM) or transmission electron microscopy (TEM). The TCDD-treated and control kidneys showed the same pattern of staining for fibronectin, but TCDD-treated kidneys displayed a diminished overall intensity. The intensity of laminin and type IV collagen immunofluorescence also appeared to be decreased, and deviations in the pattern of antibody binding were detected for differentiating TCDD-treated nephrons. Binding of the laminin antibody to the basal lamina was decreased in the parietal layer of Bowman's capsules in more advanced stages of differentiation. TEM analysis focused on the basal lamina of the tubules and Bowman's capsule. In TCDD-exposed kidneys, ECM components adjacent to differentiating nephrons were less abundant, and the basal lamina of the developing Bowman's capsules had a diminished lamina densa. The earliest nephrons to develop display these defects and comprise the first functional filtration units of the metanephric kidney. These ultrastructural changes noted in TCDD-exposed nephrons may promote proteinuria, a condition normally observed in the developing kidney when the filtration barrier is immature.

The effect of prenatal methylmercury administration on postnatal renal functional development

In utero exposure of rats to methylmercury has been reported to produce degenerative and hyperplastic changes in renal proximal and distal tubules, although no assessment of postnatal renal functional capacity was made. CH3HgCl was administered ip to Sprague-Dawley rats on Day 8 of gestation at 4 or 6 mg Hg/kg or on Days 8, 10, and 12 at 4 mg Hg/kg (3 x 4 mg Hg/kg). These doses produced no overt toxicological effects nor had any effect on litter size, body weight, or kidney weight to body weight ratios. The concentration of mercury in kidneys, liver, and brain at 1 and 7 days postpartum was dose-related but was not detectable at 42 days. In vitro renal function was assessed in renal cortical slices from rats at 1, 7, and 42 days postpartum by determining the ability to accumulate organic ions and to generate glucose. Additionally, parameters of in vivo renal function were determined in normopenic, hydropenic (5 pressor units/kg ADH, sc, 18 hr water deprived), and in volume-loaded male rats at 42 days postpartum. At 42 days postpartum in the 3 x 4 mg Hg/kg treatment group, p-aminohippurate accumulation was depressed slightly as was the ability to eliminate Na+ and water in volume-loaded rats. These data suggest that postnatal renal physiological sequelae to prenatal administration of methylmercury may be less than predicted from histological studies.

Morphometric, biochemical, and physiological assessment of perinatally induced renal dysfunction

Three chemicals, known either to alter renal development when administered during fetal development or to affect renal function when administered to adult rats, were administered to Sprague-Dawley rats at critical periods of renal development. Chlorambucil (CHL) was administered ip on d 11 of gestation at doses of 0, 3, and 6 mg/kg; nitrofen (2,4-dichlorophenyl p-nitrophenyl ether) (NIT) was given po on d 8-16 of gestation at 0, 4.17, 12.5, and 25 mg/kg . d; and mercuric chloride (MER) was given sc on postnatal d 1 at 0, 14, and 28 micrograms/pup. To assess the effects of these toxicants on the functional development of the kidneys, a diuresis test with and without antidiuretic hormone was applied on postnatal d 3 (PD 3); a hydropenia test on PD 6; and kidney weights, glomerular counts in midhilar cross sections, and the specific activity of renal alkaline phosphatase were determined on PD 3 and 6. Data from pups with obvious malformations of the kidneys was eliminated from the statistical analyses of the data so that emphasis could be placed on alterations of functional development in individuals with apparently morphologically normal kidneys. CHL retarded the growth and biochemical differentiation of the kidney at 6 mg/kg. Pups from this treatment groups showed an attenuated response to exogenously administered antidiuretic hormone. NIT impaired growth and altered renal morphology at a dose of 12.5 mg/kg . d and altered physiological responses in the absence of anatomical changes at a dose of 4.17 mg/kg . d. MER, at doses near the maximum tolerated, failed to alter any parameter, indicating that the very young animal differs markedly from the adult in response to that compound. The data indicate that relatively simple tests of renal function are useful in the detection of perinatally induced nephrotoxicity.

The heart and diaphragm: target organs in the neonatal death induced by nitrofen (2,4-dichlorophenyl-p-nitrophenyl ether)

This paper examines the effects of in utero exposure to 2,4-dichlorophenyl-p-nitrophenyl ether (nitrofen) on the viability of neonatal Long-Evans rats. Oral administration of this herbicide on days 8-18 of gestation reduced neonatal survival and birth weight. Day 11 of gestation was the most sensitive day for induction of neonatal mortality; 116 mg/kg to the dam on this day was the LD50 for the neonate. An increased incidence of hydronephrosis was observed in 35-day survivors. This increase was dose-related in animals exposed on day 11 of gestation. Fetuses exposed on day 11 and examined at term had reduced weights, delayed skeletal ossification, and an increased frequency of hydronephrosis and diaphragmatic hernias. While nitrofen did cause a high incidence of hydronephrosis, BUN or creatinine levels in 4-h neonates were not elevated. Detailed examination of the hearts of term fetuses revealed cardiac malformations classified as ventricular septal defect, double outlet right ventricle, and transposition of the great vessels. We conclude from these studies that the heart and the diaphragm are the target organs in nitrofen-induced neonatal death.

Postnatal morphology and functional capacity of the kidney following prenatal treatment with dinoseb in rats

Dinoseb has produced alterations that are suggestive of renal damage in mice and rats. Therefore it was of interest to determine the postnatal morphology and functional capacity of the kidney following prenatal treatment with dinoseb in rats. Fetal and neonatal rats treated with dinoseb on gestational d 10-12 had dilated renal pelves and ureters. Kidneys had dilated tubules and excessive mesenchymal tissue when examined perinatally. These pathological changes were reduced in incidence (kidney) or not detected (ureter) at 42 d postpartum and were not correlated with alterations in postnatal renal function. Livers from rats treated prenatally with dinoseb were vacuolated and necrotic even at 42 d postpartum. Rats treated prenatally with dinoseb had reduced body weights at 1 and 7 d postpartum. However, body weights of control and dinoseb-treated rats were not significantly different at 42 d of age. These results emphasize the need to determine the pesistence and functional consequences of anomalies detected in near-term fetuses for safety assessment of a chemical.