Substances known or suspected to cause subtle or transient anatomical alterations in renal development were administered prenatally or neonatally to rats in order to determine whether they are ...capable of altering renal functional development. Colchicine alters mitotic activity and cytoskeletal structure and is teratogenic in many species. Since the kidney of the newborn rat undergoes extensive cellular proliferation and nephron differentiation, it is possible that neonatal administration of colchicine may affect nephron development. Dinoseb and methyl salicylate have previously been reported to produce a high incidence of dilated renal pelvis in the term rat fetus. Colchicine was injected sc, at 75 micrograms/kg, to Postnatal Day (PD) 1 Sprague-Dawley rats. Dinoseb was administered ip to pregnant Sprague-Dawley rats on Gestation Days 10-12 at doses of 8 or 10.5 mg/kg/day, and methyl salicylate was administered ip at doses of 200, 250, or 300 mg/kg/day on Gestation Days 11-12. Renal function was examined in pups from immediately after birth through weaning. Maximal urine concentrating ability was measured after DDAVP (desmopressin acetate, a vasopressin analog) injection in suckling rats, and after 24 hr of water deprivation in weanlings. Proximal tubule transport was measured in renal cortical slices. Basal urinary parameters, including urine flow, osmolality, pH, and chloride content, were measured. Colchicine treatment had no effect on body weight or kidney weight. There was a significant decrease in maximal urine osmolality in PD 30 rats measured after 24 hr of water deprivation. The urine concentrating deficit detected in functionally mature PD 30 rats suggests that colchicine treatment during renal histogenesis causes a latent deficit in medullary function in the absence of any gross morphological effects. The 10.5 mg/kg/day dose of dinoseb caused a weight reduction in neonates which persisted after weaning. Urine volume after DDAVP challenge was increased over controls in both dose groups on PD 6, but maximal urine concentration was unaffected. On PD 14, maximal urine concentration after DDAVP injection was decreased in the 10.5 mg/kg/day group. By PD 30, urine concentrating ability was comparable to controls. Renal cortical slices from the 10.5 mg/kg/day dose group had an enhanced ability to accumulate organic anions on PD 3 and 31, but opposite effects were observed in the low-dose group. No other renal functional parameters were altered. Urine osmolality after DDAVP challenge was decreased over controls in the 250 mg/kg/day methyl salicylate group on PD 6, and urine volume was increased in this group after DDAVP injection on PD 14.
The fungicide dinocap is currently used in the control of powdery mildew. We have reported that dinocap is teratogenic in the CD-1 mouse, causing cleft palate, otolith defects, and fetal weight ...deficits well below maternotoxic dose levels. In this study the maternal and fetal toxicity of dinocap was determined in the Sprague-Dawley rat and Syrian golden hamster, and adult-to-developmental (A/D) toxicity ratios were calculated and compared with the previously established A/D ratio of dinocap in the mouse. Dinocap in corn oil was administered by gavage to pregnant rats on gestation days 7-20 (0, 100, 150, 200 mg/kg/day) and to hamsters on gestation days 7-14 (0, 12.5, 25, 50, 75, 100, 200 mg/kg/day). Dams were killed on day 21 (rat) or day 15 (hamster), and litters were removed, counted, and weighed; half of each litter was necropsied for soft tissue defects, and the remaining half was processed for skeletal examination. In the rat, maternal extrauterine weight gain was significantly affected at 150 and 200 mg/kg/day, relative liver weight was elevated at 100 mg/kg/day and above, and fetal weight was lower at 150 and 200 mg/kg/day. In the hamster, maternal extrauterine weight was lower at 12.5 mg/kg/day and above; fetal weight was reduced, and the incidence of dilated renal pelvis was higher, at 25 mg/kg/day and above. Thus the A/D ratios for dinocap in the rat and hamster are similar, approximately 1.
Technical-grade dinocap, a complex-mixture fungicide, is teratogenic in the CD-1 mouse, causing cleft palate and otolith defects. In this study we compared the developmental toxicities of ...2,4-dinitro-6-(1-methylheptyl)phenyl crotonate and 2,6-dinitro-4-(1-methylheptyl)phenyl crotonate, model isomers of the major active ingredients of technical dinocap, to the known teratogenicity of the technical compound. Individual isomers, both isomers combined, or technical dinocap were administered to pregnant mice on days 7-16 of gestation. Some dams were killed at term and litters were removed, dead fetuses and resorptions were counted, and live fetuses were weighed and preserved in Bodian's fixative for examination for cleft palate. Other treated dams were allowed to give birth: postnatal viability and growth, development of swimming behavior, and otolith formation were evaluated. As in previous studies, technical-grade dinocap caused cleft palate and weight deficits in fetuses at term and increased neonatal mortality and abnormal swimming behavior, torticollis, and deficient otolith formation in surviving pups. Neither of the purified isomers exhibited any developmental toxicity when administered under identical conditions. Thus, it is concluded that these isomers are not the active teratogenic component(s) in technical-grade dinocap.
The present study is an evaluation of the developmental toxicity of dinocap in three rodent species using an in vivo teratology screen. Our protocol uses postnatal viability, weight gain, and ...morphological and behavioral development through weaning to assess the developmental toxicity of compounds. Dinocap administered orally on days 7 to 16 of gestation to the CD-1 mouse resulted in increased postnatal mortality at 25 mg/kg/d (80% in block 1 and 40% in block 2). Many of the treated pups that died during the neonatal period were "ballooned" and had cleft palates. Although there was no treatment related mortality in the 12 mg/kg/d dosage group, 6% (14/226) of these mice and 24% (23/96) of the survivors from the 25 mg/kg/d dosage group displayed torticollis (a twisting of the neck resulting in an abnormal tilting of the head). These tilted-head mice held the head and forepart of the body tilted constantly to one side, both when resting and walking. The tilt was in either direction but was always constant for a given animal; in different mice, the angle varied considerably from almost 0 to 30 degrees. Some mice circled repeatedly in one direction in the home cage, others bobbed their heads and did back-flips, while others rolled over, always rolling in the same direction. In the hamster, developmental toxicity was seen at (100 and 200 mg/kg/d) or near (50 mg/kg/d) maternally toxic doses but no behavioral alterations were noted and none of the pups were ballooned.
The technique of whole embryo culture developed by New Environ Health Perspect 18:105-110, 1976 provides a sensitive assay to evaluate the effects of a test chemical on embryo development independent ...of maternal influences. To detect proteratogens, this assay must be coupled with an exogenous metabolic activation system. We have developed methods for the co-cultivation of rat embryos with primary hepatocytes, which offers several advantages over subcellular fractions when providing metabolic activation for in vitro assays. In the present study, rat embryos removed from the dam on day 10 of pregnancy were co-cultivated in vitro with primary cultures of rat, rabbit, or hamster hepatocytes. Embryos co-cultivated with hepatocytes developed normally, as did embryos exposed to a test chemical, cyclophosphamide (CP) in the absence of hepatocytes. When embryos were co-cultivated with hepatocytes and exposed to CP, a dose-related embryotoxicity was observed, indicating metabolic activation of the proteratogen. Using hepatocytes isolated from rats pretreated in vivo with phenobarbital, we observed an increase in CP-induced malformations and embryotoxicity compared to those of embryos exposed to CP in the presence of uninduced hepatocytes. The teratogenic bioactivation of CP was inhibited in vitro by the addition of metyrapone. When similar numbers of hepatocytes were used for metabolic activation of CP the induced embryotoxicity was greater in the presence of rabbit and hamster hepatocytes than with rat hepatocytes. Development of procedures for the culture of rat embryos with hepatocytes from other species suggests the utility of this in vitro system for the investigation of species differences in sensitivity to chemical teratogens.
The effects of postnatal methyl mercury exposure on the ontogeny of renal and hepatic responsiveness to trophic stimuli were examined. Increased ornithine decarboxylase (ODC) activity was used as an ...index of tissue stimulation. In the rat, renal ODC responsiveness to growth hormone, angiotensin, vasopressin, isoproterenol, and serotonin was absent at birth and matured 3 to 4 weeks later. However, pups exposed to methyl mercury showed marked, ODC responses to these same agents as early as 10 to 19 days of postnatal age, accompanied by a significant renal hypertrophy. In contrast to the kidney, the liver of normally developing rats was responsive to trophic factors even in the neonate. In this tissue, there was no consistent effect of neonatal methyl mercury treatment on ODC responses at any developmental stage tested; although absolute liver weights were reduced, liver/body weight ratio was not affected. These results demonstrate that postnatal methyl mercury exposure causes a precocious onset of ODC responses to trophic agents specifically in the kidney. Altered responsiveness may mediate some of the effects of this organomercurial on overall renal development and function.
