RESUMO
During 2020, The European Chemicals Agency (ECHA) began evaluating the OECD Test Guideline 443: Extended One Generation Reproductive Toxicity Study (EOGRTS) to analyze specific aspects related to study design, conduct and toxicological findings. A significant outcome of this ECHA evaluation focused on adequate dose level selection. Subsequently, ECHA published recommendations for DART studies, however, these recommendations seemingly do not align with the principles of the 3Rs, animal welfare or human safety goals, specifically, regarding three aspects. First, the requirement to segregate testing for sexual function and fertility from the ability to produce normally developing offspring increases the risk of inadequate identification of postnatal hazards for development and sexual function and fertility, therefore failing human health protection goals. Second, the current ECHA high-dose level setting recommendations for EOGRTS exceed the MTD (Maximum Tolerated Dose), and therefore compromise the interpretation of the biological response relative to the intrinsic effect of the chemical under evaluation. Third, the combination of these aspects will result in an increase in the number of animals tested, increasing animal welfare concerns. This paper reflects the consensus of subject matter experts, professional, and scientific societies who have authored and signed on to this statement. The signatories encourage ECHA to adopt a revised science-driven approach to the dose selection criteria that strikes a balance between regulatory vigilance and scientific pragmatism.
Assuntos
Relação Dose-Resposta a Droga , Reprodução , Testes de Toxicidade , Animais , Reprodução/efeitos dos fármacos , Testes de Toxicidade/métodos , Testes de Toxicidade/normas , Humanos , Organização para a Cooperação e Desenvolvimento Econômico , Bem-Estar do Animal , Feminino , Medição de Risco , Guias como Assunto , Substâncias Perigosas/toxicidadeRESUMO
The first Stakeholder Network Meeting of the EU Horizon 2020-funded ONTOX project was held on 13-14 March 2023, in Brussels, Belgium. The discussion centred around identifying specific challenges, barriers and drivers in relation to the implementation of non-animal new approach methodologies (NAMs) and probabilistic risk assessment (PRA), in order to help address the issues and rank them according to their associated level of difficulty. ONTOX aims to advance the assessment of chemical risk to humans, without the use of animal testing, by developing non-animal NAMs and PRA in line with 21st century toxicity testing principles. Stakeholder groups (regulatory authorities, companies, academia, non-governmental organisations) were identified and invited to participate in a meeting and a survey, by which their current position in relation to the implementation of NAMs and PRA was ascertained, as well as specific challenges and drivers highlighted. The survey analysis revealed areas of agreement and disagreement among stakeholders on topics such as capacity building, sustainability, regulatory acceptance, validation of adverse outcome pathways, acceptance of artificial intelligence (AI) in risk assessment, and guaranteeing consumer safety. The stakeholder network meeting resulted in the identification of barriers, drivers and specific challenges that need to be addressed. Breakout groups discussed topics such as hazard versus risk assessment, future reliance on AI and machine learning, regulatory requirements for industry and sustainability of the ONTOX Hub platform. The outputs from these discussions provided insights for overcoming barriers and leveraging drivers for implementing NAMs and PRA. It was concluded that there is a continued need for stakeholder engagement, including the organisation of a 'hackathon' to tackle challenges, to ensure the successful implementation of NAMs and PRA in chemical risk assessment.
Assuntos
Rotas de Resultados Adversos , Inteligência Artificial , Animais , Humanos , Testes de Toxicidade , Medição de Risco , BélgicaRESUMO
For toxicology testing of (agro)chemicals, different study types are being performed with general and/or reproductive toxicity endpoints (see Organisation for Economic Co-operation and Development guidelines). In most of these rat studies, vaginal cytology is performed on serial samples (collected by lavage) for evaluation of cycle regularity and evidence of mating, and/or on a single sample collected on the day of necropsy for information on the estrous cycle stage and allowing correlation with histopathology. In the latter case, the utility of vaginal cytology can be argued. In this article, estrous cycle stages based on vaginal cytology of samples taken on the day of necropsy and histopathology of ovaries, uterus, and vagina (gold standard for estrous cycle stage assessment) were compared. The agreement was generally low. Disagreement between the two methods could be explained by time differences between lavage and necropsy, by manipulation of vaginal epithelium during lavage which may impact epithelial morphology on histology, and by misinterpretation of vaginal cytology during or shortly after lactation. Based on the results of estrous staging within different study types, we strongly discourage vaginal cytology from samples collected on the day of necropsy since there is no added value, vaginal manipulation can be stressful and may complicate the histologic diagnosis.
Assuntos
Estro , Vagina , Animais , Epitélio , Ciclo Estral , Feminino , Ovário , Ratos , ÚteroRESUMO
The current understanding of thyroid-related adverse outcome pathways (AOPs) with adverse neurodevelopmental outcomes in mammals has been reviewed. This served to establish if standard rodent toxicity test methods and in vitro assays allow identifying thyroid-related modes-of-action potentially leading to adverse neurodevelopmental outcomes, and the human relevance of effects - in line with the European Commission's Endocrine Disruptor Criteria. The underlying hypothesis is that an understanding of the key events of relevant AOPs provides insight into differences in incidence, magnitude, or species sensitivity of adverse outcomes. The rodent studies include measurements of serum thyroid hormones, thyroid gland pathology and neurodevelopmental assessments, but do not directly inform on specific modes-of-action. Opportunities to address additional non-routine parameters reflecting critical events of AOPs in toxicological assessments are presented. These parameters appear relevant to support the identification of specific thyroid-related modes-of-action, provided that prevailing technical limitations are overcome. Current understanding of quantitative key event relationships is often weak, but would be needed to determine if the triggering of a molecular initiating event will ultimately result in an adverse outcome. Also, significant species differences in all processes related to thyroid hormone signalling are evident, but the biological implications thereof (including human relevance) are often unknown. In conclusion, careful consideration of the measurement (e.g. timing, method) and interpretation of additional non-routine parameters is warranted. These findings will be used in a subsequent paper to propose a testing strategy to identify if a substance may elicit maternal thyroid hormone imbalance and potentially also neurodevelopmental effects in the progeny.
Assuntos
Testes de Toxicidade/métodos , Rotas de Resultados Adversos , Animais , Disruptores Endócrinos , Humanos , Sistema Nervoso/efeitos dos fármacos , Sistema Nervoso/crescimento & desenvolvimento , Síndromes Neurotóxicas , Medição de Risco , Glândula Tireoide , Hormônios TireóideosRESUMO
In OECD guideline 443 - Extended One Generation Reproductive Toxicity Study (EOGRTS) - to be used for testing industrial and agrochemicals, it has been indicated that careful consideration of benefits and disadvantages should be made prior to conducting direct-dosing studies in nursing pups. Nursing pups will not be directly dosed in dietary and drinking water studies whereas in oral gavage studies this possibility exists. Besides the risk of intubation trauma and overdosing due to direct exposure and exposure via the mother's milk, direct dosing could lead to a different hazard assessment of chemicals depending on the choice of the route of administration. In addition, in case of industrial and agrochemicals used in industrial or professional settings only, there will never be direct exposure of newborns. Moreover, direct dosing of nursing pups is an artificial, non-physiological, route of exposure and as such it would hamper risk assessment. It should therefore only be considered in exceptional cases and justified on a case-by-case approach.
Assuntos
Agroquímicos/normas , Organização para a Cooperação e Desenvolvimento Econômico/normas , Testes de Toxicidade/normas , Agroquímicos/efeitos adversos , Agroquímicos/toxicidade , Animais , Animais Recém-Nascidos , Relação Dose-Resposta a Droga , Humanos , Recém-Nascido , Medição de RiscoRESUMO
The hallmark of the extended one-generation reproductive toxicity study (EOGRTS) is that, based on certain criteria or triggers, selected offspring are assigned at weaning to different cohorts for further investigation of sexual maturation, reproductive organ integrity and function, neuropathological and behavioral endpoints, and/or immune function. The triggers allow for a more customizable design based directly on the data, while minimizing animal usage. Compared to the two-generation reproductive toxicity study, the EOGRTS design increases the number, extent, and duration of F1-offspring assessments resulting in more thorough and efficient utilization of the first generation while excluding the second generation of offspring unless triggered. Therefore, the EOGRTS has the potential to reduce the number of rats required by nearly 1200 animals per study. When performing the EOGRTS, the complexity of this study should not be underestimated and experienced flexible testing laboratories with sufficient resources and historical control data for all parameters are essential. The aim of this review is to discuss the important aspects of this challenging study design and to share our knowledge on the implementation of this study in our laboratories. In addition, we elaborate on the type of criteria for expansion of the study and logistical considerations. Altogether, this review can be used as guidance by other labs, study monitors, and registration officers.
Assuntos
Reprodução/efeitos dos fármacos , Testes de Toxicidade/métodos , Animais , Estudos de Coortes , União Europeia , Regulamentação Governamental , Guias como Assunto , Ratos , Testes de Toxicidade/normasRESUMO
The extended one-generation reproduction toxicity study (EOGRTS; OECD test guideline 433) is a new and technically complex design to evaluate the putative effects of chemicals on fertility and development, including effects upon the developing nervous and immune systems. In addition to offering a more comprehensive assessment of developmental toxicity, the EOGRTS offers important improvements in animal welfare through reduction and refinement in a modular study design. The challenge to the practitioner is to know how the modular aspects of the study should be triggered on the basis of prior knowledge of a particular chemical, or on earlier findings in the EOGRTS itself, requirements of specific regulatory frameworks notwithstanding. The purpose of this document is to offer guidance on science-based triggers for these extended evaluations.
Assuntos
Fertilidade/efeitos dos fármacos , Organização para a Cooperação e Desenvolvimento Econômico , Reprodução/efeitos dos fármacos , Testes de Toxicidade/métodos , Animais , Feminino , Humanos , Sistema Imunitário/efeitos dos fármacos , Sistema Imunitário/crescimento & desenvolvimento , Masculino , Modelos Animais , Sistema Nervoso/efeitos dos fármacos , Sistema Nervoso/crescimento & desenvolvimento , Organização para a Cooperação e Desenvolvimento Econômico/normas , Ratos , Medição de Risco , Testes de Toxicidade/normasRESUMO
The predictability of the zebrafish embryo model is highly influenced by internal exposure of the embryo/larva. As compound uptake is likely to be influenced by factors such as lipophilicity, solvent use, and chorion presence, this article focuses on investigating their effects on compound distribution within the zebrafish embryo. To visualize compound uptake and distribution, zebrafish embryos were exposed for 96 hr, starting at 4 hr postfertilization, to water-soluble dyes: Schiff's reagent (logP -4.63), Giemsa stain (logP -0.77), Van Gierson stain (logP 1.64), Cresyl fast violet (logP 3.5), Eosine Y (logP 4.8), Sudan III (logP 7.5), and Oil red O (logP 9.81), with and without 1% dimethyl-sulfoxide (DMSO). Three additional compounds were used to analytically determine the uptake and distribution: Acyclovir (logP -1.56), Zidovudine (logP 0.05), and Metoprolol Tartrate Salt (logP 1.8). Examinations were performed every 24 hr. Both methods (visualization and specific analysis) showed that exposure to higher logP values results in higher compound uptake. Specific analysis showed that for lipophilic compounds >90% of compound is taken up by the embryo. For hydrophilic compounds, >90% of compound within the complete egg could not be associated to embryo or chorion and is probably distributed into the perivitelline space. Overall, internal exposure analyses on at least two occasions (i.e., before and after hatching) is crucial for interpretation of zebrafish embryotoxicity data, especially for compounds with extreme logP values. DMSO did not affect exposure when examined with the visualization method, however, this method might be not sensitive enough to draw hard conclusions.
Assuntos
Corantes/metabolismo , Dimetil Sulfóxido/farmacologia , Embrião não Mamífero/metabolismo , Desenvolvimento Embrionário/efeitos dos fármacos , Lipídeos/farmacologia , Peixe-Zebra/embriologia , Aciclovir/farmacologia , Animais , Cromatografia Líquida , Embrião não Mamífero/efeitos dos fármacos , Larva/efeitos dos fármacos , Espectrometria de Massas , Metoprolol/farmacologia , Óvulo/efeitos dos fármacos , Óvulo/metabolismo , Soluções , Zidovudina/farmacologiaRESUMO
For many years overnight fasting of rats before the collection of clinical pathology blood samples and necropsy has been a common procedure in toxicological studies for regulatory purposes. The fasting was thought to minimize the intragroup variability for clinical pathology and organ weights. However, depriving rats of food overnight will impact animal welfare by interfering with the general metabolism and may result in physiological and behavioural changes. The effects of overnight fasting in comparison to rats that were not fasted prior to necropsy was investigated in lactating rats based on an evaluation of organ weights, haematological, and clinical biochemical parameters. The results of 92 OECD 422 studies were analysed (i.e., Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test) of which approximately half of the studies incorporated fasting prior to necropsy and the other half did not. Terminal body and organ weights from all 92 studies were evaluated. Clinical pathology was included in 78 of these 92 studies. Decreased glucose levels following fasting had been reported in the literature but were not observed when comparing 39 studies with fasted conditions versus 39 studies with non-fasted conditions. Both literature and the analysed database exhibited a reduction in liver weight, alanine aminotransferase, and alkaline phosphatase levels in overnight fasted groups. These differences between fasted and non-fasted states are considered of little account as study results are always interpreted based on the differences in parameter values between treated animals compared to control animals within a study. Contrarily to previously suggested, intragroup variability was lower in the majority of parameters in non-fasted animals. According to laboratory historical data, clinical pathology and organ weight parameters are found to be very similar in male and female rats, indicating that the results of this study may be extrapolatable to non-lactating female and male rats. Based on these comparisons, it is recommended not to fast rats prior to necropsy but to continue feeding all rats ad libitum, to minimize physiological changes in these animals, to reduce variability, improve animal welfare and thereby improve the scientific value of study results.
RESUMO
Zebrafish embryo assays are used by pharmaceutical and chemical companies as new approach methodologies (NAMs) in developmental toxicity screening. Despite an overall high concordance of zebrafish embryo assays with in vivo mammalian studies, false negative and false positive results have been reported. False negative results in risk assessment models are of particular concern for human safety, as developmental anomalies may be missed. Interestingly, for several chemicals and drugs that were reported to be false negative in zebrafish, skeletal findings were noted in the in vivo studies. As the number of skeletal endpoints assessed in zebrafish is very limited compared to the in vivo mammalian studies, the aim of this study was to investigate whether the sensitivity could be increased by including a skeletal staining method. Three staining methods were tested on zebrafish embryos that were exposed to four teratogens that caused skeletal anomalies in rats and/or rabbits and were false negative in zebrafish embryo assays. These methods included a fixed alizarin red-alcian blue staining, a calcein staining, and a live alizarin red staining. The results showed a high variability in staining intensity of larvae exposed to mammalian skeletal teratogens, as well as variability between control larvae originating from the same clutch of zebrafish. Hence, biological variability in (onset of) bone development in zebrafish hampers the detection of (subtle) treatment-related bone effects that are not picked-up by gross morphology. In conclusion, the used skeletal staining methods did not increase the sensitivity of zebrafish embryo developmental toxicity assays.
Assuntos
Embrião não Mamífero , Teratogênicos , Testes de Toxicidade , Peixe-Zebra , Animais , Peixe-Zebra/embriologia , Teratogênicos/toxicidade , Embrião não Mamífero/efeitos dos fármacos , Testes de Toxicidade/métodos , Coloração e Rotulagem , Osso e Ossos/efeitos dos fármacos , Osso e Ossos/anormalidades , Desenvolvimento Embrionário/efeitos dos fármacos , Fluoresceínas/toxicidade , Antraquinonas/toxicidadeRESUMO
The rabbit prenatal developmental toxicity study is an international testing requirement for the identification and characterisation of the potential hazards of chemicals to human health. The importance of the rabbit for the detection of chemical teratogens is without question. However, the rabbit when used as a laboratory test species presents unique challenges affecting data interpretation. The purpose of this review is to identify the factors which may impact the behaviour of the pregnant rabbit and lead to significant inter-animal variability, confounding interpretation of maternal toxicity. Additionally, the importance of appropriate dose selection is discussed not least because of the conflicting guidance for identifying and defining acceptable maternal toxicity that lack reference to the rabbit in particular. The test guideline prenatal developmental toxicity study is often unable to distinguish between developmental effects as a consequence of maternal toxicity and those that are a direct effect of the test chemical on the offspring yet there is increasing pressure to use the highest possible dose levels to induce significant maternal toxicity which for the rabbit, a species little understood in toxicological terms and one that is highly susceptible to stress, is defined by very few endpoints. Interpretation of study data is further confounded by dose selection yet the developmental effects, even in the presence of maternal toxicity, are being used in Europe as the basis for classifying agents as reproductive hazards and the maternal effects are being used to define key reference values.
Assuntos
Crescimento e Desenvolvimento , Teratogênicos , Gravidez , Animais , Feminino , Coelhos , Humanos , Teratogênicos/toxicidade , Europa (Continente)RESUMO
The Extended-One-Generation Study [EOGRTS, OECD 443] is a study in which the toxic effects of test substances on reproduction (Cohort 1), neurodevelopment (Cohort 2), and development of the immune system (Cohort 3) in rats are evaluated. The latter two Cohorts are not always required according to the European Chemicals Agency (ECHA) based on data from previously performed toxicity studies. Although the Cohorts for developmental neurotoxicity (DNT) and developmental immunotoxicity (DIT) are often omitted, the F1-animals normally required for these Cohorts are still maintained for evaluation of sexual maturation since three F1-animals/sex/litter/group are required according to OECD Guidance Document (GD) No. 151. This review investigates whether two F1-animals/sex/litter/group would suffice for this endpoint by investigating the rationale provided by the GD and by comparing results of eighteen EOGRTSs in which three versus two F1-animals/sex/litter/group were evaluated. After a comprehensive literature research, we concluded that the rationale in the GD does not substantiate the decision to use three F1-animals/sex/litter/group. The scientific papers provided as rationale focused on male observations and the observations discussed do not match the observations for sexual maturation mentioned by the guidelines. The investigation using data from eighteen EOGRTSs showed that the toxicological conclusions, whether the test substance affected sexual maturation or not, matched when comparing data of two F1-animals/sex/litter/group to three F1-animals/sex/litter/group. To conclude, two F1-animals/sex/litter/group would suffice for the evaluation of sexual maturation, which negates the requirement for a so called "Cohort 1 C" (i.e. 160 animals (80 males and 80 females)) per EOGRTS, as well as the number of regulated procedures that need to be performed.
Assuntos
Reprodução , Maturidade Sexual , Animais , Estudos de Coortes , Feminino , Humanos , Sistema Imunitário , Masculino , Ratos , Testes de Toxicidade/métodosRESUMO
The possible impact on classification and labelling decisions of effects observed in second generation parental (P1) and offspring (F2) parameters in multi-generation studies was investigated. This was done for 50 substances classified as reproductive toxicants in Europe, for which a multi-generation study was available. The P1 and F2 effects were compared to parental (P0) and first generation offspring (F1) effects with regard to type of effect as well as incidence, magnitude and severity (IMS), at any dose level. For every study with unique P1/F2 effects, or differences in IMS, the influence of the P1/F2 findings on the classification decision was investigated. Unique P1/F2 generation findings did not play a crucial role in the classification decision of any of the 50 classified substances, except for fenarimol. This substance however provided abundant alerts on the basis of its endocrine activity and developmental neurotoxicity and would therefore also be expected to be identified as a developmental neurotoxicant in an Extended One Generation Reproductive Toxicity Study (EOGRTS). These findings, in addition to the increased number of parameters analysed, increased statistical power and reduced animal use, provide strong further support for replacement of the classical two-generation reproductive toxicity study by the EOGRTS in regulatory reproductive toxicity assessment.
Assuntos
Efeito de Coortes , Substâncias Perigosas/toxicidade , Exposição Paterna/efeitos adversos , Efeitos Tardios da Exposição Pré-Natal , Reprodução/efeitos dos fármacos , Testes de Toxicidade/métodos , Experimentação Animal , Animais , Sistema Endócrino/efeitos dos fármacos , Europa (Continente) , Feminino , Substâncias Perigosas/classificação , Masculino , Camundongos , Sistema Nervoso/efeitos dos fármacos , Síndromes Neurotóxicas/etiologia , Gravidez , Rotulagem de Produtos/métodos , RatosRESUMO
Recently several OECD test guidelines were updated to include thyroid hormone measurements for assessing endocrine disruptor potency, which led to an imperative need to align interpretation of these results by the different stakeholders. We therefore evaluated 124 repro screening studies, which showed in 38% of the studies a statistical significant finding for T4 in at least one treatment group, probably due to disturbances of normal homeostasis causing high variation. Consequently, for a thorough evaluation it is extremely important to take the historical control range into account. In conclusion, the current testing approach is not providing specific information needed to assess endocrine disruption, as too often a statistical significant finding is noted and as down-stream adverse effects are not evaluated. Therefore, major modifications are urgently needed. Instead of extending the in vivo experiments, it should be investigated if in vitro assessments will provide more relevant information on human endocrine disruptor potential.
Assuntos
Guias como Assunto/normas , Organização para a Cooperação e Desenvolvimento Econômico/normas , Hormônios Tireóideos/sangue , Animais , Disruptores Endócrinos/toxicidade , União Europeia , Feminino , Humanos , Masculino , Ratos , Glândula Tireoide/efeitos dos fármacos , Tireotropina/sangue , Tiroxina/sangue , Toxicologia/métodos , Toxicologia/normas , Tri-Iodotironina/sangue , Estados UnidosRESUMO
Predicting embryotoxicity of pharmaceutical compounds or industrial chemicals is crucial for public safety. Conventional studies which monitor embryo-fetal development in rats and rabbits are costly and time consuming. Alternative assays which are simpler and less costly are being pursued. The purpose of this research was to assess the capacity for the zebrafish development assay to predict mammalian plasma levels that are embryotoxic. Previously published data on rat plasma levels associated with embryotoxicity were used to guide concentration ranges for each of 25 chemicals dissolved in the media bathing developing zebrafish embryos. Embryotoxic media concentrations were compared to embryotoxic rat plasma concentrations. Assays were conducted in parallel at multiple sites as a consortium effort through the Health and Environmental Sciences Institute (HESI). Considering results from all sites, the zebrafish embryo development assay predicted (within 1-log) the rat maternal exposure levels associated with embryotoxicity 75% of the time.
Assuntos
Embrião não Mamífero , Desenvolvimento Embrionário , Testes de Toxicidade , Peixe-Zebra , Animais , Animais Geneticamente Modificados , Embrião de Mamíferos , Feminino , Desenvolvimento Fetal , Masculino , Preparações Farmacêuticas/sangue , RatosRESUMO
We evaluated the incidence of omphalocele, a malformation that occurs sporadically in many studies. We assembled data on external malformations using all treatment groups from every study published in three major journals over the past 35 years using New Zealand White rabbits. Fifty-eight papers were included: 4905 litters and 36,977 fetuses. Omphalocele was reported in 43% and was among the most common defects, occurring at a rate of 1.10% (litter) and 0.16% (fetus). The defect did not appear to be treatment-related, although it may have been in two studies, based on rate and dose-responsiveness. Removing these two studies from the analysis, the defect was still prevalent (0.77% litter, 0.11% fetal incidence). Three studies evaluated the effects of food restriction and omphalocele was observed with food restriction in two of them, suggesting that decreased maternal weight gain or food consumption may be causal. Otherwise, it appears to be spontaneous and common.
Assuntos
Anormalidades Congênitas/etiologia , Anormalidades Congênitas/veterinária , Hérnia Umbilical/etiologia , Hérnia Umbilical/veterinária , Animais , Ingestão de Alimentos , Feminino , Gravidez , Coelhos , Testes de Toxicidade , Aumento de PesoRESUMO
Many chemicals are going through a hazard-based classification and labeling process in Europe. Because of the significant public health implications, the best science must be applied in assessing developmental toxicity data. The European Teratology Society and Health and Environmental Sciences Institute co-organized a workshop to consider best practices, including data quality and consistency, interpretation of developmental effects in the presence of maternal toxicity, human relevance of animal data, and limits of chemical classes. Recommendations included larger historical control databases, more pharmacokinetic studies in pregnant animals for dose setting and study interpretation, generation of mechanistic data to resolve questions about whether maternal toxicity is causative of developmental toxicity, and more rigorous specifications for what constitutes a chemical class. It is our hope that these recommendations will form the basis for subsequent consensus workshops and other scientific activities designed to improve the scientific robustness of data interpretation for classification and labeling.
Assuntos
Guias como Assunto/normas , Substâncias Perigosas/classificação , Rotulagem de Produtos , Teratogênicos/classificação , Teratologia/normas , Toxicologia/normas , Humanos , Rotulagem de Produtos/legislação & jurisprudência , Rotulagem de Produtos/normasRESUMO
In recent years several OECD test guidelines have been updated and some will be updated shortly with the requirement to measure thyroid hormone levels in the blood of mammalian laboratory species. There is, however, an imperative need for clarification and guidance regarding the collection, assessment, and interpretation of thyroid hormone data for regulatory toxicology and risk assessment. Clarification and guidance is needed for 1) timing and methods of blood collection, 2) standardization and validation of the analytical methods, 3) triggers for additional measurements, 4) the need for T4 measurements in postnatal day (PND) 4 pups, and 5) the interpretation of changes in thyroid hormone levels regarding adversity. Discussions on these topics have already been initiated, and involve expert scientists from a number of international multisector organizations. This paper provides an overview of existing issues, current activities and recommendations for moving forward.
Assuntos
Técnicas de Laboratório Clínico/normas , Disruptores Endócrinos/toxicidade , Guias como Assunto/normas , Reprodução/efeitos dos fármacos , Hormônios Tireóideos/sangue , Testes de Toxicidade , Animais , Técnicas de Laboratório Clínico/métodos , Feminino , Masculino , Padrões de Referência , Testes de Função Tireóidea , Glândula Tireoide/efeitos dos fármacos , Testes de Toxicidade/métodos , Testes de Toxicidade/normasRESUMO
Since adoption of the first globally implemented guidelines for developmental and reproductive toxicity (DART) testing for pharmaceuticals, industrial chemicals and agrochemicals, many years passed without major updates. However in recent years, significant changes in these guidelines have been made or are being implemented. These changes have been guided by the ethical drive to reduce, refine and replace (3R) animal testing, as well as the addition of endocrine disruptor relevant endpoints. Recent applied improvements have focused on reduction and refinement. Ongoing scientific and technical innovations will provide the means for replacement of animal testing in the future and will improve predictivity in humans. The aim of this review is to provide an overview of ongoing global DART endeavors in respect to the 3Rs, with an outlook towards future advances in DART testing aspiring to reduce animal testing to a minimum and the supreme ambition towards animal-free hazard and risk assessment.
Assuntos
Alternativas aos Testes com Animais , Teratogênicos/toxicidade , Testes de Toxicidade/métodos , AnimaisRESUMO
Routinely in many laboratories, satellite rats are added to embryo-fetal development (EFD) studies for pharmaceuticals to assess toxicokinetic (TK) properties, because it is assumed that collection of multiple blood samples with relatively large volumes might affect the study outcome. With recent refinement of blood sampling techniques, this belief requires reevaluation. The current work showed successful implementation of jugular vein blood sampling in an EFD rat study without satellite animals, thereby reducing the number of rats in standard EFD studies for pharmaceuticals by 20%. Although not evaluated in this study, microsampling has shown to be very successful and eliminates the need of satellite animals. However, currently not all laboratories have implemented this method and regularly the bioanalytical method is already developed with a limit of quantification that is insufficiently sensitive. Therefore in those cases, a quick win to omit satellite animals can be established by using jugular vein blood sampling.