28-day Repeated-dose Toxicity Research Articles

Corn rootworm-active RNA DvSnf7: Repeat dose oral toxicology assessment in support of human and mammalian safety

Genetically modified (GM) crops have been developed and commercialized that utilize double stranded RNAs (dsRNA) to suppress a target gene(s), producing virus resistance, nutritional and quality traits. MON 87411 is a GM maize variety that leverages dsRNAs to selectively control corn rootworm through production of a 240 base pair (bp) dsRNA fragment targeting for suppression the western corn rootworm (Diabrotica virgifera virgifera) Snf7 gene (DvSnf7). A bioinformatics assessment found that endogenous corn small RNAs matched ∼450 to 2300 unique RNA transcripts that likely code for proteins in rat, mouse, and human, demonstrating safe dsRNA consumption by mammals. Mice were administered DvSnf7 RNA (968 nucleotides, including the 240 bp DvSnf7 dsRNA) at 1, 10, or 100 mg/kg by oral gavage in a 28-day repeat dose toxicity study. No treatment-related effects were observed in body weights, food consumption, clinical observations, clinical chemistry, hematology, gross pathology, or histopathology endpoints. Therefore, the No Observed Adverse Effect Level (NOAEL) for DvSnf7 RNA was 100 mg/kg, the highest dose tested. These results demonstrate that dsRNA for insect control does not produce adverse health effects in mammals at oral doses millions to billions of times higher than anticipated human exposures and therefore poses negligible risk to mammals.

Analysis of public oral toxicity data from REACH registrations 2008-2014.

SummaryThe European Chemicals Agency, ECHA, made available a total of 13,832 oral toxicity studies for 8,568 substances up to December 2014. 75% of studies were from the retired OECD Test Guideline 401 (11% TG 420, 11% TG 423 and 1.5% TG 425). Concordance across guidelines, evaluated by comparing LD50 values ≥ 2,000 or < 2,000 mg/ kg bodyweight from chemicals tested multiple times between different guidelines, was at least 75% and for their own repetition more than 90%.In 2009, Bulgheroni et al. created a simple model for predicting acute oral toxicity using no observed adverse effect levels (NOAEL) from 28-day repeated dose toxicity studies in rats. This was reproduced here for 1,625 substances. In 2014, Taylor et al. suggested no added value of the 90-day repeated dose oral toxicity test given the availability of a low 28-day study with some constraints. We confirm that the 28-day NOAEL is predictive (albeit imperfectly) of 90-day NOAELs, however, the suggested constraints did not affect predictivity.1,059 substances with acute oral toxicity data (268 positives, 791 negatives, all Klimisch score 1) were used for modeling: The Chemical Development Kit was used to generate 27 molecular descriptors and a similarity-informed multilayer perceptron showing 71% sensitivity and 72% specificity. Additionally, the k-nearest neighbors (KNN) algorithm indicated that similarity-based approaches alone may be poor predictors of acute oral toxicity, but can be used to inform the multilayer perceptron model, where this was the feature with the highest information value.

Is a 14-day dose setting study able to predict its 28-day repeated dose toxicity?

Is a 14-day dose setting study able to predict its 28-day repeated dose toxicity?

Abstract W P70: Pharmacokinetic Properties and Toxicity/safety Profiles of SP-8203, a Novel Neuroprotectant for Treatment of Cerebral Ischemic Stroke

We recently identified a multi-target directed neuroprotectant SP-8203, which is now undergoing phase 1 clinical trial. Here we report the preclinical and clinical toxicity/safety profiles and pharmacokinetic properties of SP-8203. Single-dose and 28-day repeated-dose toxicity tests in Sprague Dawley rats, Beagle dogs, and Cynomolgus monkeys were performed by Chemon (Korea), MPI Research (USA), and Toxikon (USA) and Phase 1 clinical trial by ASAN medical center (korea). The genotoxicity was examined by the bacterial reverse mutation assay (AMES test), the chromosome aberration assay using Chinese hamster ovary and lung cells, and the micronucleus test in rat bone-marrow erythrocytes. The safety pharmacology studies evaluate acute neurobehavioral toxicities and pulmonary functions in male rats and cardiovascular toxicities in male Cynomolgus monkeys. Following a single-dose intravenous administration, the minimum lethal dose of SP-8203 was estimated to 60 mg/kg and the lethal dose 50 (LD50) was 83.3 mg/kg in rats. The No-Observable-Adverse-Effect-Level (NOAEL) of 4 week repeated dose of SP-8203 was 20 mg/kg/day in rats and 12 mg/kg/day in monkeys, when administered as an intravenous slow bolus injection for 5 min. However, when administered as an intravenous infusion for 30 min, the NOAEL in rats increased to 80 mg/kg/day or more. SP-8203 did not exert any genotoxicity. Safety pharmacology studies showed that NOAELs of neurobehavioral toxicity, pulmonary functions, and cardiovascular effects were 30 mg/kg, 30 mg/kg, and 10 mg/kg, respectively. In a single accelerating dose study in phase 1 clinical trial, no toxic responses were observed at doses up to 240mg in healthy subjects. Pharmacokinetics of SP-8203 evaluated after its intravenous administration in humans and rats showed that the AUCs and half-lives of SP-8203 were dose-dependently increased; thus the dose-normalized AUCs and half-lives were significantly elevated with increasing doses. However, the nonlinear PK properties are within safe ranges in humans and rats. Taken together, a series of toxicity/safety assessments showed that SP-8203 is quite safe and non-toxic at the doses for the treatment of cerebral ischemic stroke in humans.

Evaluation of vinyl laurate in a battery of in vitro and in vivo tests for genotoxicity

Vinyl laurate is a potential residual monomer in chewing gum base formulated with polyvinyl acetate vinyl laurate copolymer (PVAcVL). The genotoxic potential of vinyl laurate was examined in a battery of in vitro and in vivo genotoxicity tests. Vinyl laurate was not mutagenic in Ames tests. In addition, it was not mutagenic in the HPRT mutation assay in L5178Y cells. An in vitro mammalian chromosome aberration assay performed in CHO cells was equivocal. Vinyl laurate and/or its metabolites were not clastogenic in the mouse bone marrow micronucleus test. Kinetic data indicate that VL is metabolised to acetaldehyde and lauric acid. Both metabolites are well known and have been studied previously. Model calculations show, that any exposure to acetaldehyde from the consumption of PVAcVL containing chewing gum will remain far below levels of acetaldehyde exposure from food in which acetaldehyde occurs naturally. Direct exposure to VL will primarily be at the site of entry. The lack of toxicity in a 90-day repeated dose toxicity test, performed with VL doses up to approximately 3000 times higher than the maximal VL intake from the consumption of a typical piece of chewing gum, demonstrates a high safety margin.

90-day repeated dose toxicity and genotoxicity tests of evodia officinalis

90-day repeated dose toxicity and genotoxicity tests of evodia officinalis

Toxicological profile of ultrapure 2,2',3,4,4',5,5'-heptachlorbiphenyl (PCB 180) in adult rats.

PCB 180 is a persistent non-dioxin-like polychlorinated biphenyl (NDL-PCB) abundantly present in food and the environment. Risk characterization of NDL-PCBs is confounded by the presence of highly potent dioxin-like impurities. We used ultrapure PCB 180 to characterize its toxicity profile in a 28-day repeat dose toxicity study in young adult rats extended to cover endocrine and behavioral effects. Using a loading dose/maintenance dose regimen, groups of 5 males and 5 females were given total doses of 0, 3, 10, 30, 100, 300, 1000 or 1700 mg PCB 180/kg body weight by gavage. Dose-responses were analyzed using benchmark dose modeling based on dose and adipose tissue PCB concentrations. Body weight gain was retarded at 1700 mg/kg during loading dosing, but recovered thereafter. The most sensitive endpoint of toxicity that was used for risk characterization was altered open field behavior in females; i.e. increased activity and distance moved in the inner zone of an open field suggesting altered emotional responses to unfamiliar environment and impaired behavioral inhibition. Other dose-dependent changes included decreased serum thyroid hormones with associated histopathological changes, altered tissue retinoid levels, decreased hematocrit and hemoglobin, decreased follicle stimulating hormone and luteinizing hormone levels in males and increased expression of DNA damage markers in liver of females. Dose-dependent hypertrophy of zona fasciculata cells was observed in adrenals suggesting activation of cortex. There were gender differences in sensitivity and toxicity profiles were partly different in males and females. PCB 180 adipose tissue concentrations were clearly above the general human population levels, but close to the levels in highly exposed populations. The results demonstrate a distinct toxicological profile of PCB 180 with lack of dioxin-like properties required for assignment of WHO toxic equivalency factor. However, PCB 180 shares several toxicological targets with dioxin-like compounds emphasizing the potential for interactions.

CARCINOscreen®: New short-term prediction method for hepatocarcinogenicity of chemicals based on hepatic transcript profiling in rats.

Carcinogenicity is one of the most serious toxic effects of chemicals, and highly accurate methods for predicting carcinogens are strongly desired for human health. Here, we developed a new prediction system named "CARCINOscreen®" for evaluating the carcinogenic potentials of chemicals using the gene expression profiles of liver tissues from rats after a 28-day repeated dose toxicity study.The prediction formula was generated using a support vector machine with predictive genes selected from 68 training chemical datasets; a predictive score was then calculated to predict the carcinogenic potentials of the tested chemicals. To ensure the accuracy of the prediction system, the chemicals were divided into three groups (Groups 1 to 3) according to the resulting hepatic gene expression profiles, and a prediction formula was generated for each group. The prediction system was capable of predicting the carcinogenicity of training carcinogens and non-carcinogens with an accuracy of 92.9% to 100%. The final prediction result was determined based on the maximum prediction value obtained with three independent prediction formulas to build up the CARCINOscreen®. The system was able to predict carcinogenicity accurately in 94.1% of the 68 training chemicals. An external validation trial was performed with 16 chemicals, consisting of various carcinogens targeting rat liver or other organs and non-carcinogens. The system identified 68.8% of all the chemicals and 100% of the rat liver carcinogens as carcinogens. Thus, the CARCINOscreen®, a novel system for predicting hepatocarcinogenicity, is a promising tool for the prediction of rat liver carcinogens.

Immunotoxicity of silver nanoparticles in an intravenous 28-day repeated-dose toxicity study in rats

BackgroundNanosilver is used in a variety of medical and consumer products because of its antibacterial activity. This wide application results in an increased human exposure. Knowledge on the systemic toxicity of nanosilver is, however, relatively scarce. In a previous study, the systemic toxicity of 20 nm silver nanoparticles (Ag-NP) was studied in a 28-day repeated-dose toxicity study in rats. Ag-NP were intravenously administered with a maximum dose of 6 mg/kg body weight (bw)/day. Several immune parameters were affected: reduced thymus weight, increased spleen weight and spleen cell number, a strongly reduced NK cell activity, and reduced IFN-γ production were observed.MethodsPrompted by these affected immune parameters, we wished to assess exposure effects on the functional immune system. Therefore, in the present study the T-cell dependent antibody response (TDAR) to keyhole limpet hemocyanin (KLH) was measured in a similar 28-day intravenous repeated-dose toxicity study. In addition, a range of immunological parameters was measured. Data obtained using the benchmark dose (BMD) approach were analyzed by fitting dose-response models to the parameters measured.ResultsA reduction in KLH-specific IgG was seen, with a lowest 5% lower confidence bound of the BMD (BMDL) of 0.40 mg/kg bw/day. This suggests that Ag-NP induce suppression of the functional immune system. Other parameters sensitive to Ag-NP exposure were in line with our previous study: a reduced thymus weight with a BMDL of 0.76 mg/kg bw/day, and an increased spleen weight, spleen cell number, and spleen cell subsets, with BMDLs between 0.36 and 1.11 mg/kg bw/day. Because the effects on the spleen are not reflected by increased KLH-specific IgG, they, however, do not suggest immune stimulation.ConclusionsIntravenous Ag-NP administration in a 28-day repeated-dose toxicity study induces suppression of the functional immune system. This finding underscores the importance to study the TDAR to evaluate immunotoxicity and not to rely solely on measuring immune cell subsets.

An antioxidant, N,N′-diphenyl-p-phenylenediamine (DPPD), affects labor and delivery in rats: A 28-day repeated dose test and reproduction/developmental toxicity test

A 28-day repeated dose toxicity test and reproduction/developmental toxicity test for N,N'-diphenyl-p-phenylenediamine (DPPD) were conducted in [Crl:CD(SD)] SPF rats. Male and female rats were dosed with DPPD by gavage for 28 days at 0, 100, 300, or 1000 mg/kg bw/day or for a total of 42-46 days at 0, 8, 50, or 300 mg/kg bw/day. No significant adverse effects were observed in the repeated dose toxicity study up to 1000 mg/kg bw/day in both sexes. In the reproduction/developmental toxicity study, two females showed piloerection, hypothermia, and pale skin; one died and the other showed dystocia on day 23 of pregnancy at 300 mg/kg bw/day. Another female delivered only three live pups at 300 mg/kg bw/day. A significantly prolonged gestation period was observed at 50 and 300 mg/kg bw/day. The NOAELs of repeated dose toxicity and reproduction/developmental toxicity were considered to be 1000 and 8 mg/kg bw/day, respectively.

Reproducibility and robustness of metabolome analysis in rat plasma of 28-day repeated dose toxicity studies

BASF has developed a rat plasma metabolomics database (MetaMap®Tox) containing the metabolome of more than 500 chemicals, agrochemicals and drugs, for which the toxicity is well known, derived from 28-day repeated dose toxicity studies in rats. The quality/reproducibility of data was assessed by comparing the metabolome of 16 reference compounds tested at least twice under identical experimental conditions at three time points (day 7, day 14 and day 28). Statistical correlation analysis showed that the repeated treatment induced very similar changes to the metabolome. For all repetitions the modes of action of the compounds were always correctly identified. Moreover, when compared against the metabolome of all compounds available in the MetaMap®Tox database, the repetitions showed in most cases the highest degree of overall similarity with the metabolome of the original study. In addition, we also evaluated the robustness of our metabolomics technique, displayed by constancy of variability in control groups over time. Based on these results, it can be concluded, that metabolomics can reproducibly be applied during toxicological in vivo testing in rats under the conditions applied here.

Endocrine-Mediated Effects of a Benzophenone Related Chemical, 2,3,4,4'-Tetrahydroxybenzophenone, Based on Uterotrophic Assay, Hershberger Assay, and Subacute Oral Toxicity Study

The purpose of this study was to investigate the endocrine-mediated effects of a benzophenone-relative compound, 2,3,4,4’-tetrahydroxybenzophenone, based on the OECD protocols. In the uterotrophic assay, female SD rats were subcutaneously injected with the chemical at doses of 0, 100, 300, and 1,000 mg/kg on each of 3 days from postnatal day 20 to day 22, and the uterine weight of rats given the 300 and 1,000 mg/kg doses of the test chemical increased. In the Hershberger assay, the test chemical was orally administered at doses of 0, 60, 200, and 600 mg/kg/day to castrated male SD rats for 10 consecutive days beginning on postnatal day 56, and no changes were observed. On the other hand, when the test chemical was orally administered at doses 0, 60, 200, and 600 mg/kg/day for at least 28 days, serum T4 values decreased in male rats in the 600 mg/kg group. This suggests a mechanism of action related to the inhibition of thyroid peroxidase. The uterotrophic assay used in this study showed that the chemical has estrogen-agonist properties, however, estrogenic effects were not observed in a 28-day repeated-dose toxicity study. On the other hand, endocrine-mediated effects such as thyroid hormone dysfunction were detected in growing rats based on the results of the OECD test guideline No. 407.

Development of safety profile evaluating pharmacokinetics, pharmacodynamics and toxicity of a combination of pioglitazone and olmesartan medoxomil in Wistar albino rats

Pioglitazone (PIO), an antidiabetic drug and olmesartan medoxomil (OLM), an antihypertensive drug were administered orally alone and in combination to Wistar albino rats for evaluation of pharmacokinetics, pharmacodynamics and repeated dose 28-day oral toxicity of individual drugs and their combination. Pharmacokinetic study was performed by orally administering PIO and OLM at single dose of 3 and 2mg/kg, respectively alone and in combination analyzing the plasma samples using LC–MS/MS. Antidiabetic activity evaluation was done in type-2 diabetes mellitus induced animals at same dose level as in pharmacokinetic study daily for 30days. PIO and/or OLM were administered orally to animals at daily doses of 50, 100 and 150mg/kg for 28days for toxicity study. There was no significant alteration in the pharmacokinetic parameters of either drug indicating absence of any pharmacokinetic interaction when co-administered. Positive pharmacodynamic interaction between PIO and OLM was established in this study. Two drugs in combination showed no evidence of potentiation of 28-day repeated dose toxicity in animals. Again, drugs, alone and in combination, caused only minor changes in clinical-laboratory tests and histopathological change was not found in the experiment performed. In conclusion, PIO and OLM combination can primarily be stated as safe in terms of present toxicity and pharmacokinetics findings.

Acute and 28-day repeated dose toxicology studies in mice with aryloxyalkanoate dioxygenase (AAD-1) protein expressed in 2,4-D tolerant DAS-40278-9 maize

DAS-40278-9 maize (corn) plants have been genetically modified by the insertion of the aad-1 gene (aryloxyalkanoate dioxygenase), which confers tolerance to 2,4-dichlorophenoxyacetic acid (2,4-D) and aryloxyphenoxypropionate (AOPP) acetyl coenzyme A carboxylase (ACCase) inhibitors (“fop” herbicides) to enable the effective use of these herbicides on maize. The aad-1 gene, derived from Sphingobium herbicidovorans, encodes the aryloxyalkanoate dioxygenase (AAD-1) enzyme. As part of the safety assessment of the AAD-1 protein expressed in maize, acute and repeated dose mammalian toxicology studies were conducted. AAD-1 protein (heterologously produced) was orally administered to mice at a dose of 2000mg/kg, and no acute lethality or adverse effects were observed. Similarly, no adverse effects were observed in mice in a 28-day repeated-dose dietary toxicity study that incorporated the AAD-1 protein into diets at concentrations up to 1000-fold greater than the highest estimate of human exposure to maize. These results support the conclusion that the AAD-1 protein, as expressed in biotechnology derived DAS-40278-9 maize, represents a negligible risk to human health.

A safety study of a B‐class CpG ODN in Sprague–Dawley rats

Oligodeoxynucleotides containing CpG motifs (CpG ODNs) are potent immune activators and are being tested as anti-tumor, antimicrobial agents and as adjuvants in vaccines. Little has been reported, however, about the systematic and comprehensive safety evaluation on repeated CpG ODN administration. To investigate the safety profile of a newly developed CpG ODN, CpG 684, we conducted a 28-day repeated dose toxicity study in rats, at dose levels of 5, 20 and 150 µg CpG 684 per rat. No abnormalities in clinical observations, growth, urinalysis and bone marrow cell counts were found in CpG 684 treated rats. CpG 684 was proved biologically active, capable of up-regulating the expressions of CD40 and CD86 molecules. The monocyte numbers were increased at the dose levels of 20 and 150 µg per rat. The spleen weights were increased in female rats at the dose level of 150 µg per rat. Microscopically, 5, 20 and 150 µg per rat CpG 684 caused local inflammatory cell infiltration and hyperplasia of fibrous tissue at injection sites; the treatment of 5 and 150 µg per rat CpG 684 induced enhanced inflammatory reaction in inguinal lymphoid tissue, and the dose of 150 µg per rat induced cell hyperplasia in white pulp of spleen and white pulp expansion. CpG 684 at 150 µg per rat led to decreases in peripheral lymphocyte, serum globulin, glucose, alkaline phosphatase and K+ levels in female rats, and induced the decrease in serum albumin and total protein in rats of both sexes. The data from this study will provide an important reference for developing CpG 684 as an adjuvant for vaccines of human use.

A Spontaneous Teratocarcinoma in the Testis of a Swiss Albino Mouse

A unilateral non-metastatic embryonal carcinoma and teratoma of the testis was observed in a 12-week-old Swiss Albino mouse at the end of a 28-day repeated dose toxicity study. The teratocarcinoma almost completely replaced the parenchyma of the left testis. The tumor was composed of sheets and rosettes of primitive embryonal cells, anaplastic cells, skeletal muscle tissue, sebaceous gland tissue, keratinized stratified squamous epithelium, and ciliated cuboidal epithelium. The histomorphological characteristics of the tumor were reviewed and presented in this report. To the best of the authors' knowledge, this is the first report of spontaneous teratocarcinoma of testis in the Swiss Albino strain of mice.

Influence of coefficient of variation in determining significant difference of quantitative values obtained from 28-day repeated-dose toxicity studies in rats

In order to understand the influence of coefficient of variation (CV) in determining significant difference of quantitative values of 28-day repeated-dose toxicity studies, we examined 59 parameters of 153 studies conducted in accordance with Chemical Substance Control Law in 12 test facilities. Sex difference was observed in 12 parameters and 10 parameters showed large CV in females. The minimum CV was 0.74% for sodium. CV of electrolytes was comparatively small, whereas enzymes had large CV. Large differences in CV were observed for major parameters among 7-8 test facilities. The changes in CV were grossly classified into 11. Our study revealed that a statistical significant difference is usually detected if there is a difference of 7% in mean values between the groups and the groups have a CV of about 7%. A parameter with a CV as high as 30% may be significantly different, if the difference of the mean between the groups is 30%. It would be ideal to use median value to assess the treatment-related effect, rather than mean, when the CV is very high. We recommend using CV of the body weight as a standard to judge the adverse effect level.

Preliminary safety assessment of Yarrowia lipolytica extracellular lipase: Results of acute and 28-day repeated dose oral toxicity studies in rats

Interest in extracellular lipase sourced from the non conventional yeast Yarrowia lipolytica has increased over the last decade. The enzyme was recently suggested as a good candidate for pancreatic exocrine insufficiency treatment. However, there is still a lack of oral safety evaluation data. In this work, we conducted acute and 28-day repeated dose toxicity studies in rats. Both male and female rats were first orally treated with fungal lipase at either single or repeated doses. The results demonstrated that neither single dose nor chronic administration of lipase was associated with mortality or abnormalities in general conditions, behavior and growth. Except a decrease in urine pH and a dose-unrelated increase of triglycerides observed in males, chronic administration of lipase resulted in similar hematological, blood biochemical and urine parameters to those of untreated animals. Minor histopathological changes were observed in lungs and livers of treated and untreated animals but they were considered of no toxicological significance. This study provides, for the first time, safety data on Yarrowia lipolytica extracellular lipase that support its use as a pharmaceutical.

Safety assessment of N-acetyl-l-threonine

N-acetyl-l-threonine (NAT) is a dietary constituent that has been identified at low concentrations (<1μg/g fresh weight) in numerous foods. The current paper reports the outcome of toxicology studies conducted to assess the effects of NAT. No evidence of mutagenicity or genotoxicity was observed in in vitro bacterial or in vivo mammalian studies. No mortalities or evidence of adverse effects were observed in Sprague–Dawley (SD) rats following acute oral administration of 2000mg of NAT/kg of body weight (kg of bw). A 28-day repeated dose toxicity study was conducted in SD rats by incorporating NAT into diets at concentrations targeting up to 1000mg of NAT/kg of bw/day. All rats survived until scheduled sacrifice and no biologically significant differences were observed in any of the NAT treatment groups for body weights, feed consumption, clinical signs, behavioral, ophthalmology, hematology, coagulation, clinical chemistry, organ weights, or gross or microscopic changes. Based on these results, NAT does not represent a risk for mutagenicity or genotoxicity, is not acutely toxic, and the no-observed-adverse-effect-level (NOAEL) for systemic toxicity from repeated dose dietary exposure to NAT is 848.5 and 913.6mg/kg of bw/day for male and female SD rats, respectively.

Enhanced OECD TG 407 in detection of endocrine-mediated effects of 4,4′-(octahydro-4,7-methano-5H-inden-5-ylidene)bisphenol

The purpose of this study was to investigate whether the estrogenic effects were detected in the enhanced TG 407 if the estrogenic property was not so strong in the uterotrophic assay. The estrogenic property of 4,4'-(octahydro-4,7-methano-5H-inden-5-ylidene)bisphenol in the uterotrophic assay was slightly stronger than that of genistein or nonylphenol, but weaker than that of ethinyl estradiol. We performed a 28-day repeated-dose toxicity study (enhanced OECD test guideline No. 407) on 4,4'-(octahydro-4,7-methano-5H-inden-5-ylidene)bisphenol based on the OECD draft protocol. The test chemical, administered orally at doses of 0, 10, 50, and 250 mg/kg per day for at least 28 days, caused such estrogenic effects as abnormal estrous cycle, increased ovarian follicles, increased uterine epithelial height, and vaginal mucification in the 50 and/or 250 mg/kg groups. Moreover, follicular epithelial cell hyperplasia of the thyroid was detected in all male rats given the test chemical and in female rats in the 250 mg/kg group. It was concluded that the estrogenic effects were detected in growing rats given 4,4'-(octahydro-4,7-methano-5H-inden-5-ylidene)bisphenol, and thyroid dysfunction was also observed as the endocrine-mediated effects.