A Collaborative Study in Japan on Optimal Treatment Period and Parameters for Detection of Male Fertility Disorders Induced by Drugs in Rats

Update of the risk assessment on 3-monochloropropane diol and its fatty acid esters

The CONTAM Panel updated the assessment of the risks for human health related to the presence of 3-monochloropropane diol (3-MCPD) and its fatty acid esters in food published in 2016 in view of the scientific divergence identified in the establishment of the tolerable daily intake (TDI) in the Joint FAO/WHO Expert Committee on Food Additives and Contaminants (FAO/WHO) report published in 2017. In this update, dose-response analysis was performed following the recent EFSA Scientific Committee guidance on the use of benchmark dose (BMD) approach in risk assessment, and a review of available data on developmental and reproduction toxicity was included. The outcome of this review indicates that in rats short-term exposure to 3-MCPD above 1 mg/kg body weight (bw) per day can induce reduced sperm motility associated with reduced male fecundity. Decreased sperm count and histopathological changes in the testis and epididymis were observed following longer treatment periods at higher doses. Regarding increased incidence kidney tubular hyperplasia, BMD analysis using model averaging resulted in a BMDL 10 of 0.20 mg/kg bw per day in male rats, which was selected as the new Reference Point (RP) for renal effects. For the effects on male fertility, decreased sperm motility was selected as the most sensitive relevant endpoint and a BMDL 05 of 0.44 mg/kg bw per day was calculated. The RP for renal effects was considered to derive an updated group TDI of 2 μg/kg bw per day for 3-MCPD and its fatty acid esters and was considered protective also for effects on male fertility. The established TDI of 2 μg/kg bw per day is not exceeded in the adult population. A slight exceedance of the TDI was observed in the high consumers of the younger age groups and in particular for the scenarios on infants receiving formula only.

Ultrastructural analysis of early toxic effects produced by bee venom phospholipase A2 and melittin in Sertoli cells in rats

In this study, we aimed to investigate the testicular toxicity of two molecules derived from bee venom (BV): phospholipase A2 (PlA2) and melittin (Mlt). Ultrastructural effects of purified BV PlA2 and Mlt were assessed consecutive to repeated dose (30 days) and acute toxicity studies. For the subchronic treatment, PlA2 and Mlt were injected in daily doses equivalent to those released by a bee sting (105 μg PlA2/kg/day and 350 μg Mlt/kg/day), while in the acute treatment their doses corresponded to those released by 100 bee stings (9.3 mg PlA2/kg and 31 mg Mlt/kg). Both PlA2 and Mlt affected the Leydig cells and the cells in seminiferous tubules, the Sertoli cells first of all. PlA2 injection resulted in detachment of the Sertoli cells from the surrounding cells, and extracellular vacuolations, cytoplasmic vacuolations in their basal region and in branches as well, detachment of spermatids, residual bodies and sometimes even spermatocytes into the lumen, changes that had a higher magnitude after the acute treatment. Mlt injection induced similar ultrastructural alterations, but more severe, including degeneration of cellular organelles and cellular necrosis, resulting into rarefaction of the seminiferous epithelium; the ultrastructural changes had a higher magnitude after the 30 repeated dose treatment. We concluded that either of the two molecules tested here, PlA2 and Mlt, were Sertoli cells toxicants at the used doses, and they participated both in the BV testicular toxicity. We consider the observed changes as part of a preceding mechanism of the more severe alterations produced by the BV. It also remains possible that these early unspecific changes reported here could represent the response of the SCs not only to the components of bee venom, but to molecules of other venoms as well. The Sertoli cells were the primary target of PlA2 and Mlt in the spermatogenic epithelium, and their alteration led to further degenerative changes of the germ cells. Since the exposure to PlA2 and Mlt caused severe alteration, including cell death and detachment of immature germ cells into the lumen, we may also conclude that the bee venom molecules had a potential to interfere with normal progression of spermatogenesis. All the degenerative changes observed in the Sertoli cells were accompanied with changes of the Leydig cells.

Histopathological and ultrastructural changes experimentally induced by bee venom in seminiferous epithelium via structural-functional alteration of Sertoli cells

We tested here the ability of bee venom (BV) to interfere with spermatogenesis in rats in two experimental conditions. The histopathological changes were assessed with brightfield microscopy using a novel staining technique, based on methylene blue, orange G and ponceau xylidine. Transmission electron microscopy was also used to identify fine subcellular changes. BV injection for 30days in daily doses of 700μg BV/kg resulted in reducing testicular weight, along with significant larger diameters of seminiferous tubules and reduced number of Sertoli cells (SCs). SCs were vacuolated, detached from the basement membrane, many necrosed, leading to the basement membrane denudation. Germ cells layers were separated by empty spaces conferring a rarefied aspect to the tissue, and spermatids were detached into lumen. Thus, the seminiferous epithelium was significantly thinned. Many Leydig cells (LCs) were in a necrotic state, with disrupted plasma membrane and without smooth endoplasmic reticulum. The acute treatment with a single LD50 of 62mgBV/kg, was followed by focal disruptions of the basement membrane and localized areas of necrosis, mainly affecting the SCs. Most of the observed SCs as well as some spermatogonia were highly vacuoled, empty spaces being observed within the epithelium. The SCs count was significantly decreased. Spermatids had also the tendency of separation from the SCs, and the significant larger diameter of the tubules found was associated with a thicker epithelium. Many LCs were necrosed, with disrupted plasma membrane, swollen mitochondria, no endoplasmic reticulum and implicitly showing rarefied cytoplasm. We concluded that BV was a testicular toxicant affecting both the LCs and the seminiferous tubules. The SCs cells represented the primary target site of BV whose effects were next extended upon the germ cells. In all cells, BV triggered unspecific degenerative changes that could impaire spermatogenesis. The present study also proposes an alternative staining technique very useful in assessing the histopathological aspects of spermatogenesis.

Improvements in Clinical Trials Information Will Improve the Reproductive Health and Fertility of Cancer Patients

There are a number of barriers that result in cancer patients not being referred for oncofertility care, which include knowledge about reproductive risks of antineoplastic agents. Without this information, clinicians do not always make recommendations for oncofertility care. The objective of this study was to describe the level of reproductive information and recommendations that clinicians have available in clinical trial protocols regarding oncofertility management and follow-up, and the information that patients may receive in clinical trials patient information sheets or consent forms. A literature review of the 71 antineoplastic drugs included in the 68 clinical trial protocols showed that 68% of the antineoplastic drugs had gonadotoxic animal data, 32% had gonadotoxic human data, 83% had teratogenic animal data, and 32% had teratogenic human data. When the clinical trial protocols were reviewed, only 22% of the protocols reported the teratogenic risks and 32% of the protocols reported the gonadotoxic risk. Only 56% of phase 3 protocols had gonadotoxic information and 13% of phase 3 protocols had teratogenic information. Nine percent of the protocols provided fertility preservation recommendations and 4% provided reproductive information in the follow-up and survivorship period. Twenty-six percent had a section in the clinical trials protocol, which identified oncofertility information easily. When gonadotoxic and teratogenic effects of treatment were known, they were not consistently included in the clinical trial protocols and the lack of data for new drugs was not reported. Very few protocols gave recommendations for oncofertility management and follow-up following the completion of cancer treatment. The research team proposes a number of recommendations that should be required for clinicians and pharmaceutical companies developing new trials.

Repeated exposure to iron oxide nanoparticles causes testicular toxicity in mice

The aim of this study was to determine whether repeated exposure to iron oxide nanoparticles (Fe₂ O₃ -NPs) could be toxic to mice testis. Fe₂ O₃ -NPs (25 and 50 mg/kg) were intraperitoneally administered into mice once a week for 4 weeks. Our study showed that Fe₂ O₃ -NPs have the ability to cross the blood-testis barrier to get into the testis. The findings showed that exposure resulted in the accumulation of Fe₂ O₃ -NPs which was evidenced from the iron content and accumulation in the testis. Furthermore, 25 and 50 mg/kg Fe₂ O₃ -NPs administration increased the reactive oxygen species, lipid peroxidation, protein carbonyl content, glutathione peroxidase activity, and nitric oxide levels with a concomitant decrease in the levels of antioxidants-superoxide dismutase, catalase, glutathione, and vitamin C. Increased expression of Bax, cleaved-caspase-3, and cleaved-PARP confirms apoptosis. Serum testosterone levels increased with increased concentration of Fe₂ O₃ -NPs exposure. In addition, the histopathological lesions like vacuolization, detachment, and sloughing of germ cells were also observed in response to Fe₂ O₃ -NPs treatment. The data from our study entailed that testicular toxicity caused by Fe₂ O₃ -NPs exposure may be associated with Fe₂ O₃ -NPs accumulation leading to oxidative stress and apoptosis. Therefore, precautions should be taken in the safe use of Fe₂ O₃ -NPs to avoid complications in the fertility of males. Further research will unravel the possible molecular mechanisms on testicular toxicity of Fe₂ O₃ -NPs. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 594-608, 2017.

Revision of the ICH guideline on detection of toxicity to reproduction for medicinal products: SWOT analysis

SWOT analysis was used to gain insights and perspectives into the revision of the ICH S5(R2) guideline on detection of toxicity to reproduction for medicinal products. The current ICH guideline was rapidly adopted worldwide and has an excellent safety record for more than 20 years. The revised guideline should aim to further improve reproductive and developmental (DART) safety testing for new drugs. Alternative methods to animal experiments should be used whenever possible. Modern technology should be used to obtain high quality data from fewer animals. Additions to the guideline should include considerations on the following: limit dose setting, maternal toxicity, biopharmaceuticals, vaccines, testing strategies by indication, developmental immunotoxicity, and male-mediated developmental toxicity. Emerging issues, such as epigenetics and the microbiome, will most likely pose challenges to DART testing in the future. It is hoped that the new guideline will be adopted even outside the ICH regions.

Nonclinical reproductive toxicity testing requirements for drugs, pesticides, and industrial chemicals in India and China

India and China have booming chemical, agrochemical, and pharmaceutical industries. Both countries also represent expanding markets for foreign chemical and healthcare companies. All such products require reproductive toxicity testing before marketing. The ICH testing guidelines for medicinal products are not applicable in China and India. Nonetheless, reproductive toxicity studies designed and run to ICH principles are generally acceptable for submission. The Chinese guidelines take into consideration traditional Chinese medicines, which are usually mixtures. Likewise, the specific recommendations of India and China for the reproductive toxicity testing of chemicals and pesticides differ from those of the OECD and the USEPA. Again, studies performed in accordance with internationally recognized principles are usually acceptable for submission in both countries. The Chinese guideline for the reproductive toxicity testing of agrochemicals is currently under revision; the new version is expected to resemble more closely the requirements of the OECD and the USEPA. As a member of the OECD, India has conducted Good Laboratory Practice (GLP) inspection, accreditation, and monitoring activities since 2004. China has made several attempts to join the Council Decisions on Mutual Acceptance of Data in the Assessment of Chemicals since 2005. Currently 47 laboratories in China have been certified by the national GLP authorities. Several laboratories in China have also been recently been certified by OECD member countries as GLP compliant. In India, there are currently 23 GLP-Certified laboratories; about six of these are also AALAC accredited. The specific study designs specified in the guidelines of China and India for reproductive toxicity studies are described in detail in this chapter.

Toxic effects of Carthamus tinctorius L. (Safflower) extract on mouse spermatogenesis

OBJECTIVE

To evaluate the effects of aqueous extract of Carthamus tinctorius L., also named safflower, on mouse spermatogenesis.

METHODS

Sixteen adult male NMRI mice were used. Experimental group received Carthamus tinctorius L. extract at the dose of 200 mg/kg for 35 consecutive days and control group received only distilled water. Testicular histopathology, morphometric analysis and spermatogenesis assessments were performed for evaluation of the Carthamus tinctorius L. extract effects on testis.

RESULTS

Histopathological criteria such as epithelial vacuolization, sloughing of germ and detachment were significantly decreased in Carthamus tinctorius L. treated mice (p < 0.001). Carthamus tinctorius L. extract induced formation of multinucleated giant cells in the germinal epithelium. Carthamus tinctorius L. extract also caused a significant decrease in seminiferous tubule diameter, seminiferous epithelium height and maturation arrest (p < 0.001).

CONCLUSION

Carthamus tinctorius L. extract has toxic effects on mouse testicular tissue, and recommended to use it with caution if there is a reproductive problem.

Assessment of reproductive toxicity under REACH

The European REACH regulation requires the evaluation of reproductive toxicity in screening tests according to OECD TG 421 and 422 for substances above the tonnage level of 10 tons/year. The overall aim of this paper is to increase flexibility in combination with a reduced number of experimental animals. Therefore, in contrast to the existing approach the registrant should have the possibility to file a dossier for a substance at the level of 10 tons/year and above also on the basis of data from a developmental toxicity study (OECD TG 414) plus a full-scale subacute toxicity study (OECD TG 407 according to the 1995 protocol). The proposed new test strategy takes into account overall considerations of duty of care and animal welfare. It enables an assessment of developmental toxicity on a definitive instead of a screening level. Registrants should be allowed to select between these two options, either the existing approach (OECD TG 421/407 and alternatively TG 422) or the approach proposed in this paper (OECD TG 407 plus TG 414).

A Tiered Approach to Life Stages Testing for Agricultural Chemical Safety Assessment

A proposal has been developed by the Agricultural Chemical Safety Assessment (ACSA) Technical Committee of the ILSI Health and Environmental Sciences Institute (HESI) for an improved approach to assessing the safety of crop protection chemicals. The goal is to ensure that studies are scientifically appropriate and necessary without being redundant, and that tests emphasize toxicological endpoints and exposure durations that are relevant for risk assessment. The ACSA Life Stages Task Force proposes a tiered approach to toxicity testing that assesses a compound's potential to cause adverse effects on reproduction, and that assesses the nature and severity of effects during development and adolescence, with consideration of the sensitivity of the elderly. While incorporating many features from current guideline studies, the proposed approach includes a novel rat reproduction and developmental study with enhanced endpoints and a rabbit development study. All available data, including toxicokinetics, ADME data, and systemic toxicity information, are considered in the design and interpretation of studies. Compared to existing testing strategies, the proposed approach uses fewer animals, provides information on the young animal, and includes an estimation of human exposure potential for making decisions about the extent of testing required.

Spontaneous and Age-Related Testicular Findings in Beagle Dogs

This study was conducted to characterize spontaneous testicular and epididymal microscopic findings in eighty control beagle dogs from toxicity studies. Hypospermatogenesis, characterized by randomly scattered missing spermatids and/or spermatocytes within seminiferous tubules, was observed in 75% of dogs six to seven months of age and declined to fewer than 10% in dogs over eleven months of age. Atrophy/hypoplasia of seminiferous tubules, characterized by subcapsular triangular clusters of tubules containing no germ cells, was observed in 25 to 40% of dogs under twelve months old, decreasing with age to 14 to 17% in dogs twelve to thirty-six months old. Retained spermatids, multinucleate giant cells, intracytoplasmic vacuoles (presumably in Sertoli cells), and swollen spermatocytes were common findings of minimal severity. Six- and seven-month-old dogs had lower testicular weights, less filling of the epididymal tails with sperm, and a two-fold higher incidence of abnormal epididymal content compared to dogs more than eight months of age. Most male beagles were histologically sexually mature by eight to nine months of age. This study confirms published reports that dogs at least ten months of age at necropsy usually are adequate for routine microscopic evaluation of the testes. If evaluation of spermatogenesis is critical, the incidental findings can be minimized by using males over twelve months of age.

Proteomic investigation of 1,6-dimethoxyhexane testicular toxicity

The aliphatic ether 1,6-dimethoxyhexane (DMH) was previously identified as a testicular toxicant. Testis protein extracts from control and DMH-treated rats were subjected to two-dimensional gel electrophoresis for comparison of protein expression profiles. MALDI-ToF peptide mass fingerprinting of differentially expressed proteins resulted in the conclusive identification of heat shock-related 70kDa protein 2 (HSP70.2), 60kDa heat shock protein, mitochondrial precursor (HSP60) and protein disulfide isomerase A3 precursor (ERp60). The potential involvement of these proteins in chemically induced perturbation of spermatogenesis and their utility as biomarkers of testicular toxicity are discussed in light of the knowledge currently available from the literature.

Critical aspects in reproductive and developmental toxicity testing of environmental chemicals

The process of toxicity testing of environmental chemicals is ruled by a framework of guidelines (OECD, OPPTS, etc.). The present paper will describe the process from the biological tests for environmental chemicals up to potential labelling and will focus on some critical aspects in this cascade of events. It is also the aim of this paper to give an overview of the existing documents and draft documents relevant for this field and available in the internet. Based on the current situation, the following points are discussed as critical issues: life stage considerations and their implications on testing, usefulness of investigations in juvenile animals, requirements for ADME studies, design and endpoints in fertility studies, use and usefulness of developmental milestones, performance of special studies versus one-study-design, considerations on transplacental carcinogenicity and early aging, significance of maternal/parental toxicity, application of triggers to justify studies, inclusion of new endpoints into test guidelines, and test strategies applied. Based on this, the usefulness of risk considerations in the current EU classification system for toxicity to reproduction as well as potency considerations will be discussed and suggestions will be made to improve the basic requirements for chemical testing which have remained relatively unchanged over the past 20 years.

Evaluation of a two-generation reproduction toxicity study adding endpoints to detect endocrine disrupting activity using vinclozolin

A two-generation reproduction toxicity study in rats adding extra endpoints to detect endocrine disrupting activity was conducted using vinclozolin by dietary administration at 0, 40, 200, and 1000 ppm, for investigation of its utility. The extra endpoints included anogenital distance (AGD), nipple development, sexual maturation (vaginal opening and preputial separation), estrous cycle, spermatogenesis, sex organ weights, and blood hormone concentrations (thyroid and sex hormones). Hepatic drug-metabolizing enzyme activities were also measured. The results revealed changes due to vinclozolin in the AGD, nipple development, sexual maturation, sex organ weights, and blood sex hormone concentrations in males of both parental animals and offspring, even at the lowest dose of 40 ppm, confirmed by results for the classical endpoints of histopathological examination at 200 ppm and mating at 1000 ppm. The effects on parental males included increased pituitary and testis weights, and decreased epididymis weights at 1000 ppm in both generations, and decreased prostate and epididymis weights at 200 and 1000 ppm and seminal vesicle weights at 1000 ppm in F1 males. Histopathological examination revealed hypertrophy of the basophilic cells in the pituitary at these two doses, and diffuse hyperplasia of the testicular interstitial cells and atrophy of the seminal vesicle mucosa at 1000 ppm in F0 and F1 males. In addition, F1 males demonstrated decrease in prostate fluid at 200 and 1000 ppm. Blood hormone analysis revealed increases in LH, FSH, testosterone, and DHT in F0 and F1 males at 1000 ppm. General toxicological effects included suppressed body weight gain in F0 and F1 females and in F1 males, and reduced food consumption in F0 and F1 females at 1000 ppm. Histopathological examination revealed centrilobular hepatocellular hypertrophy in males at 200 and 1000 ppm and in females at 1000 ppm, increased lipid droplets in the adrenal zona fasciculata and zona glomerulosa in males at 200 and 1000 ppm and in females at 40 ppm and above, and hyperplasia of ovarian interstitial cells and vacuolation of lutein cells in females at 1000 ppm in both generations. Almost all the tissue changes were accompanied by changes in weights. Decreases in T3 and/or T4 were observed in both sexes and generations at 1000 ppm and in F0 females at 200 ppm. However, these were presumed to be secondary to induction of hepatic drug-metabolizing enzymes, activities being increased for a range of enzymes in both sexes and generations at 1000 ppm. Rise in BROD activity was the most prominent, suggesting that vinclozolin mainly induces CYP2B. As for effects on reproductive function, a marked decrease in the fertility index caused by male infertility was observed in F1 animals at 1000 ppm. However, no effects on spermatogenesis were seen in either F0 or F1 males. Since cleft prepuce and penile hypoplasia were observed in infertile males, it is probable that the cause of infertility in F1 males was related to morphological abnormalities in the external genitalia. Vinclozolin did not affect the estrous cycle, mating, fertility, pregnancy, parturition, or nursing behavior in either F0 or F1 females. In offspring, in addition to suppressed body weight gain in F1 males and females at 1000 ppm, neonatal toxicity caused by antiandrogen activity of vinclozolin was observed in F1 and F2 males. Effects included shortened AGD in F1 males at 1000 ppm and in F2 males at 200 and 1000 ppm, and nipple/areola remnants in F1 males at 200 and 1000 ppm and in F2 males at 40 ppm and above. In addition, decreased epididymis weights at weaning and morphological abnormalities of the external genitalia, including cleft prepuce, penile hypoplasia, and vaginal pouch, were seen in F1 and F2 males at 1000 ppm.

Characterization of the effect of deoxynivalenol on selected male reproductive endpoints

The effect of deoxynivalenol (DON) exposure on male reproductive function was assessed in the rat. Male rats were divided into a control group (n=15 rats) and four treatment groups (0.5 mg/kg, n=15; 1.0 mg/kg, n=15; 2.5 mg/kg, n=15; and 5.0 mg/kg DON, n=16) and exposed to DON daily for 28 days via gastric intubation. Both body weight gain and the final body weight of animals in the 5.0 mg/kg dose group and feed consumption in animals in the 2.5 mg/kg and 5.0 mg/kg dose groups were significantly reduced compared to controls. Fluid consumption was not affected in any of the treated groups. Epididymal and seminal vesicle weights expressed per gram of body weight and brain weight were significantly reduced, compared to control weights, in animals from the 2.5 and 5.0 mg/kg dose groups while prostate weight expressed per gram of brain weight and body weight was significantly lower than controls only in the 5.0 mg/kg dose group. A statistically significant, dose-related decrease in homogenization resistant testicular spermatid counts, spermatid numbers, absolute cauda epididymal sperm numbers and cauda epididymal sperm numbers per gram of cauda epididymis was observed in the 5.0 mg/kg DON treatment group. Sperm tail abnormalities (broken tails) in the 5.0 mg/kg dose group were significantly higher than in the control group. Sperm swimming speed (VSL and VCL) was significantly increased only in the 2.5 mg/kg dose group. Serum FSH and LH concentrations were increased in a dose dependent manner across all treated groups while serum testosterone concentrations were decreased in a dose-related manner across all dose groups. An increase in germ cell degeneration, sperm retention and abnormal nuclear morphology was observed in the 2.5 mg/kg and 5.0 mg/kg dose groups. Treatment related effects included lesions in the non-glandular stomach, thymic lymphoid depletion and splenic hematopoiesis in the 5.0 mg/kg treatment group.

EVALUATION OF A TWO-GENERATION REPRODUCTION TOXICITY STUDY ADDING ENDOPOINTS TO DETECT ENDOCRINE DISRUPTING ACTIVITY USING LINDANE

A two-generation reproduction toxicity study in rats adding extra endpoints to detect endocrine disrupting activity was conducted using lindane by dietary administration at 0, 10, 60, and 300 ppm, for investigation of its utility. The extra endpoints included anogenital distance (AGD), nipple development, sexual maturation (vaginal opening and preputial separation), estrous cycle, spermatogenesis, sex organ weights, and blood hormone concentrations (thyroid and sex hormones). F1 offspring were examined for emotionality (open field test), motor coordination (rotarod test), as well as learning and memory (pole-climbing test). Hepatic drug-metabolizing enzyme activities were also measured. The results revealed general toxicological effects on parental animals, influence on reproductive function, and altered development of offspring; however, they did not demonstrate any distinct changes in the extra endpoints for detection of endocrine disrupting activity. Adult toxicity was observed in both F0 and F1 animals, including suppressed body weight gain and reduced food consumption in both sexes, and deaths of females at 300 ppm. Convulsions and irritability were observed during the perinatal period in pregnant F1 females given 300 ppm. Pathological examination revealed increased liver weights and centrilobular hepatocellular hypertrophy in both sexes and generations at 10 or 60 ppm and above; in addition, increased kidney weights and increased hyaline droplets in the proximal tubule epithelium, and basophilic renal tubules in males were noted at 10 ppm and above. Pituitary weights were decreased in F0 females and in F1 males and females and adrenal weights were increased in F1 males and females at 300 ppm; however, no histological changes were observed, and manifestations suggesting endocrine disrupting activity related to these changes were lacking. Hypertrophy of the thyroid follicular epithelium in F0 females at 300 ppm and in F1 males at 60 and 300 ppm, and decreases in T3 and/or T4 in both sexes and generations at 300 ppm were presumed to be secondary changes associated with the induction of hepatic drug-metabolizing enzymes. Blood hormone analysis revealed no changes in sex hormones attributable to lindane in males or females. Hepatic drug-metabolizing enzyme activities were increased dose-dependently from 10 ppm in both sexes and generations, with the rise in BROD activity being the most prominent. There were also increases in MROD, EROD, T-6beta-OH, and T4-UDP-GT activities (BROD >> EROD > MROD, T-6beta-OH, T4-UDP-GT). This suggests that while lindane most strongly induces CYP2B, it also upregulates a number of other drug metabolizing enzymes, such as CYP1A, CYP3A, and UDP-GT. As for effects on reproductive function, lack of maternal behavior, including lactation and retrieval behavior, and consequent total litter loss were observed in F1 dams at 300 ppm. There were no effects of lindane on the estrous cycle, spermatogenesis, mating, fertility, pregnancy, or parturition. Neonatal toxicity was observed in both sexes and generations, including suppressed body weight gain at 60 and 300 ppm, and decreased thymus and spleen weights without histological change at 300 ppm. The postnatal survival rate in F2 offspring was decreased due to lack of maternal behavior in dams at 300 ppm.

Evaluation of OECD screening tests 421 (reproduction/developmental toxicity screening test) and 422 (combined repeated dose toxicity study with the reproduction/developmental toxicity screening test)

The Advisory Committee on Existing Chemicals (BUA) of the Federal Republic of Germany convened a panel with expertise in reproductive and developmental toxicology to evaluate the OECD Screening Tests 421 (Reproduction/Developmental Toxicity Screening Test) and 422 (Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test) with respect to their ability to unmask any potential toxic effects on reproduction. The original assignment for that panel was to "validate" those screening tests. However, the panel members recognized beforehand that this was actually an impossible task because of lack of a sufficient database. Only five chemicals with known reproductive toxicity had been examined following the OECD Screening Test Guidelines 421 or 422. A comparison of these test results with those of the definitive OECD Test Guidelines 414, 415, 416, or additional investigations could, therefore, only have been made with this very limited number of chemicals that had also undergone evaluation by one of the test guidelines cited. In each case biological properties relevant to reproductive toxicity were also indicated by the OECD Screening Tests 421 or 422. This communication reviews the main differences in study design of OECD Screening Test Guidelines 421 and 422 compared to those definitive test guidelines of similar study design for reproduction or developmental toxicity (especially with the one-generation study, OECD Test Guideline 415). The very limited possibilities of detecting late postnatal and postlactational manifestations are emphasized, as is the low statistical power of the OECD Screening Tests 421 and 422. Furthermore, the very limited ability to unmask teratogenicity is delineated. The outcome of screening tests was evaluated based on the results of 57 studies conducted according to the OECD Test Guideline 421 or 422. The test results were categorized according to the incidence of toxic effects on reproduction in the parent animals or their offspring and related to general toxic effects. Based on the ranking of these results, recommendations regarding setting rational priorities for further evaluations of existing chemicals' reproductive hazards are made. In general, the reviewer panel supports the OECD position that the screening tests are useful for initial hazard assessment and can contribute to the decision-making process on setting priorities for further test requirements. The panel also agrees with the OECD statement that the OECD Screening Tests 421 and 422 are neither an alternative to definitive tests (i.e., OECD Test Guidelines 414, 415, and 416) nor are they intended as their replacement.

Some aspects relating to the evaluation of the effects of chemicals on male fertility

Reviews and studies on individual compounds were analyzed as to the suitability of different study designs and endpoints for detecting adverse effects of chemicals on male reproduction in animal species. Of the endpoints investigated, the most sensitive proved to be histopathology of the testes. Using refined histopathology, effects could be detected with a high degree of sensitivity as early as 4 weeks after treatment. Other sensitive endpoints were the weights of reproductive organs, including accessory glands, i.e., testis, epididymis, prostate, and of the seminal vesicle, as well as sperm parameters such as sperm count, sperm morphology, and sperm motility. Sperm motility was found to be in some cases more sensitive than histopathology. The above parameters showed a higher sensitivity than fertility parameters. In fact, in most cases, not only one but several endpoints were affected. Continuous breeding studies and 90-day studies with additional measurements of sperm parameters were similarly effective in detecting compounds which affect male fertility. Interspecies extrapolation factors (IEFs) have been derived for the most sensitive endpoints in laboratory animals. If the calculation is based on caloric demand and a sensitive endpoint of reproductive toxicity, many IEFs tend to be about 1, indicating that humans are generally not more susceptible to reproductive toxicants than laboratory animals. With respect to hazard identification, it is possible to detect adverse effects on male reproduction in a standard subacute study with concentrations that produce significant general toxicity. If effects are found, for the risk assessment the NOAEL has to be determined by testing specific sensitive parameters as specified above.

Lack of effects of oxolinic acid on spermatogenesis in young adult and aged Wistar rats

Prolonged treatment with oxolinic acid is known to elevate serum luteinizing hormone (LH) levels, resulting in induction of Leydig cell tumors in rats. In a carcinogenicity study of the compound, tubular atrophy of the testis was also increased, suggesting that oxolinic acid might affect spermatogenesis. The present study was therefore performed using rats of different ages with a particular focus on seminiferous tubule alteration and its relation to Leydig cell proliferation. Young adult (7 weeks of age) and aged (52 weeks of age) males of the Wistar strain were administered oxolinic acid at dietary concentrations of 0 (basal diet), 300, 1000 or 3000 ppm for 4 (all groups), 13 (0 and 3000 ppm groups), 26 (0 and 3000 ppm groups), or 52 weeks (0 and 3000 ppm groups of aged rats). Serum LH levels were elevated in both young adult and aged animals treated with 3000 ppm at most examined time points. While testosterone levels were also increased at the early time points in young adult, this was not the case in older animals. Elevation of the incidences of foci and/or focal hyperplasia of Leydig cells was noted but was only slight limited to aged rats treated with 3000 ppm after 26 weeks. Furthermore, it did not appear to be related to seminiferous tubular alteration. No treatment-related histopathological abnormalities could be detected in any treatment group, and morphometrical stage analysis of spermatogenesis conducted for the control and 3000 ppm-treated groups demonstrated no lesions. These results provide strong evidence that prolonged oxolinic treatment does not directly induce testicular toxicity or altered spermatogenesis in either young adult or aged rats, except for slight increase of Leydig cell proliferative lesions caused by elevated serum LH levels. Aged rats might have higher sensitivity than young adults to the effects of oxolinic acid on proliferative lesions of Leydig cells.

Effects of neonatal exposure to a high-dose p-tert-octylphenol on the male reproductive tract in rats

Time-course alterations in morphological changes of the reproductive tract including spermatogenesis as well as pituitary and gonadal hormones, reproductive ability, and the size of the sexually dimorphic nucleus of the preoptic area (SDN-POA) were investigated in male rats neonatally exposed to 100 mg/kg p-tert-octylphenol (OP) subcutaneously. OP treatment affected hormone levels of follicle stimulating hormone (FSH) and testosterone, reproductive organ weights and sperm counts. Slightly depressed FSH levels at prepuberty and prolonged suppression of testosterone till 7 weeks of age were observed as two hormonal alterations. The lasting reduction in testosterone appeared to be associated with growth inhibition of male reproductive organs such as the testis, prostate and epididymis, these demonstrating low organ weights compared with those of age-matched controls till 7 weeks of age. The FSH concentrations after puberty showed a rise to values equal to or higher than those of the control group, suggesting recovery of maturation of the reproductive tract. No morphological abnormalities, even with morphometric stage analysis of spermatogenesis, were detected in the male reproductive tract throughout the study. Size of the SDN-POA and reproductive ability was comparable to those in controls. At the termination (18 weeks of age), however, a reduction in the sperm count in the epididymis of OP-treated animals demonstrated a possibility that the male reproductive system might be still affected by neonatal exposure to OP. The results observed demonstrate that neonatal exposure to a high-dose OP exerts estrogenic action directly or indirectly, resulting in slight but prolonged impairment of the male reproductive tract. The suppression of FSH caused by modulation of the hypothalamus-pituitary control system may be the trigger for the impairment, while the possibility of direct estrogenic action of OP is not ruled out. Our results also indicate that more sensitive endpoints should be established to detect the effects of neonatal exposure to estrogens or estrogenic compounds on the male reproductive tract.

Improved risk assessment by screening sperm parameters

The question of whether a 4 or 9 week premating treatment period is more suitable in studies for effects on fertility and early embryonic development, and the extent to which the screening of sperm parameters may contribute to the detection of effects, has been under discussion since the ICH guideline changed in 1994/1995. This study presents a comparison between 4 and 9 weeks treatment with known male reproductive toxicants with regard to sperm motility, count, morphology, abnormal movements and testicular and epididymal histopathology. Mating outcome was examined after 4 weeks treatment. Three compounds with different targets and mechanisms of action were chosen: two testicular toxicants, Pyridoxine and Adriamycin and the epididymal toxicant, alpha-Chlorohydrine. Sperm motility was reduced in males treated with Pyridoxine (markedly) and alpha-Chlorohydrine (slightly) after 4 weeks treatment and in males treated with Adriamycin after 9 weeks treatment. With Pyridoxine and Adriamycin, sperm count was significantly increased after 4 weeks. Histopathological examination after 4 weeks showed characteristic changes leading to marked testicular tubular atrophy at 8/9 weeks, which was confirmed by a significantly reduced sperm count at 8/9 weeks. With alpha-Chlorohydrine, sperm count was not affected and the results of the histopathological examination were equivocal. Changes in sperm morphology were observed after 4/9 weeks of treatment with Pyridoxine. Mating outcome after 4 weeks was markedly affected with both Pyridoxine and alpha-Chlorohydrine, but no effect was observed with Adriamycin. The results of this study indicate that the two testicular toxicants would have been detected as male reproductive toxicants in a 4-week general toxicity study with routine testicular histopathology and examination of sperm parameters, without the need for mating trials. For the epididymal toxicant, alpha-Chlorohydrine, there was slightly reduced sperm motility after 4 weeks treatment, but mating trials were necessary for confirmation of the toxic effect. Without sperm motility examination, this effect would have been missed in early drug development causing problems in clinical studies. Further comparisons of the validity of 4 or 9 weeks treatment require the testing of other compounds with different targets/mechanism of actions, as well as evaluation of dose-response relationships.

Overview of male reproductive pathology

An understanding of form and function is important for examination of the male reproductive tract. A basic understanding of spermatogenesis and hormonal function in the reproductive tract is essential for the pathologists in this evaluation. Gross and histologic reproductive changes need to be distinguished from normal variation and correlated with the reproductive status of the animal. This is especially important when correlating histologic changes with organ weight and other reproductive parameters, such as seminal analysis data. Sexual maturity of animals and tissue handing can impact interpretation. Sexual immaturity of preclinical safety animals can present challenges for accurate identification of compound-related changes. Likewise, proper handling of unfixed reproductive tissues and appropriate selection of a fixation protocol are important in avoiding artifacts that may interfere with the microscopic evaluation. The histopathology technician needs to recognize testicular landmarks that allow for correct orientation at trimming so the pathologist can assess not only the morphology of seminiferous tubules but also the outflow tract. For the most effective evaluation of the male reproductive tract, the testes and epididymides should be examined concurrently. Although the term "staging" is often used inappropriately, the pathologist should review testicular tissues in a "stage-aware" manner. This article reviews gross and histologic changes of the male reproductive tract as well as tissue orientation and fixation to assist in accurate interpretation of potential treatment-related changes in male reproduction.

Spontaneous testicular lesions in purpose-bred beagle dogs

Spontaneous testicular lesions were assessed in 50 control purpose-bred male beagle dogs. They were selected from 13 toxicology studies conducted over the period 1988-1999. Age of the dogs at study termination varied from 8-20 months with an average age of 13 months. Regardless of age, the most significant finding was bilateral segmental hypospermatogenesis in 15/50 (30%) of the dogs. Cross sections of tubules with hypospermatogenesis were distributed randomly throughout the testes and were characterized by reduced proportions of germ cells, tubular shrinkage, and Sertoli cell prominence. These changes were occasionally associated with giant cells, with cellular debris, and in 6/15 (40%) with atrophic tubules devoid of germ cells, indicating a degenerative process. Focal subcapsular tubular atrophy or hypoplasia (tubules lined by Sertoli cells only) was also found in 9/35 (26%) of dogs without hypospermatogenesis. Inhibited spermiation with retention of mature sperm in tubules was seen in 6/50 dogs, 3 of which also showed hypospermatogenesis. Other findings of high incidence but low prevalence included tubules with multinucleated giant cells, swollen spermatocytes, or apoptotic germ cells. These latter changes are probably a constituent of normal spermatogenesis. In conclusion, about 30% of control beagle dogs show segmental hypospermatogenesis, which may be associated with degenerative changes, and an additional 18% of the dogs exhibit focal tubular atrophy/hypoplasia in otherwise normal testes. These changes have to be distinguished from compound-related toxic effects.

Influence of chlorocholinechloride-treated wheat on selected in vitro fertility parameters in male mice

The aim of this study was to evaluate the influence of feeding with food and water containing chlorocholinechloride (CCC) on the fertility of male mice in a two-generation study. For this purpose the number of testicular spermatozoa and the relative proportion of primary and secondary spermatocytes involved in spermatogenesis were measured. Furthermore, the fertility of epididymal spermatozoa from tested male mice was investigated in a special in-vitro fertilization system. The experimental food was composed of CCC-treated wheat in the first experiment and CCC-free wheat and water mixed with pure CCC in the second experiment. The CCC residue content in the treated food and water was 0.21 mg/kg and 0.2 mg/L, respectively. Under the influence of feeding with CCC-treated wheat (Experiment 1) the fertilization and cleavage rates of oocytes incubated with spermatozoa from CCC-fed mice were reduced: the fertilization rate 65.1% vs. 21.1% and the cleavage rate 51.9% vs. 20.3%, p < 0.01 (control feeding vs. CCC feeding, respectively). Feeding of sperm donors with pure CCC mixed with untreated wheat pellets or water (Experiment 2) led to a reduction in the fertilization and cleavage rate (control: 60.8%, 32.4%; CCC-food: 29.8%, 12.1%; CCC-water: 30.1%, 10.2%; CCC-food/water: 36.6%, 12.5%; p < 0.01, respectively). The normal course of spermatogenesis was unchanged after the exposure to CCC. Testicular weight, the number of spermatozoa, and the proportion of haploid, diploid, and tetraploid testicular cells were not influenced. However, the functional competence of epididymal spermatozoa from CCC-fed donors was reduced, resulting in a significantly diminished fertilization and cleavage rate in vitro. The results suggest that CCC could interfere with epididymal protein secretion and the process of sperm maturation during passage through the epididymis.

Influence of environmental cadmium on testicular proliferation in roe deer

The influence of cadmium on spermatogenesis in roe deer was studied, comparing animals from areas with high (n = 37) and low (n = 23) cadmium exposure. Testes were evaluated during pre-rut (May) and rut (July/August). During these periods the cadmium accumulation (mg/kg kidney) in polluted regions averaged 3.41 and 3.52 in comparison with 1.61 and 1.81 in controls. Cadmium accumulation was positively correlated with testis weight during both seasons. In May the proliferation (units of tissue polypeptid specific antigen/g parenchyma) was lower in animals with higher cadmium (24.02 compared with 78.20; P < 0.01). During the rut, testicular proliferation and spermatozoa/g testis as well as apoptosis showed no significant changes with increased cadmium contamination. The results suggest delayed proliferation during the pre-rutting period in animals with high cadmium exposure, but other indications of effects on the testis were not significant.

Effects of 2-bromopropane on spermatogenesis in the Sprague-Dawley rat

In 1995, 2-bromopropane (2-BP) was associated with occupational reproductive and hematopoietic toxicity in Korea. The effect of 2-BP on spermatogenesis, or Leydig cells, has not been determined in adult rats. In the present study, 40 ten-week-old Sprague-Dawley (SD) rats were treated orally with 3.5 g/kg/d of 2-BP for 3 consecutive days. At 1, 3, 5, 7, 14, 28, 42, and 70 d after treatment, testes were perfused with Karnovsky's solution or immersed in Bouin's solution, embedded in plastic or Epon and evaluated with light and electron microscopy. DNA ploidy distributions of testicular suspensions were determined by flow cytometry, which allowed comparison of quantitative spermatogenesis with histopathologic observations. Degeneration of spermatogonia was observed during Stages I-IV in seminiferous tubules on Day 1 after treatment. Spermatocytes, spermatids, Sertoli cells, and Leydig cells appeared normal in the early stage of the study. Whereas spermatid retention in Stages IX-XI was observed on Day 7 after treatment, depletion of spermatocytes and spermatids continued over time, followed by a marked increase of germ cells on Day 42 after treatment. However, the seminiferous tubules did not completely recover by study termination. Leydig cell cellularity increased mildly without any significant morphologic modification at the end of the study. Immunohistochemistry using an antibody against proliferating cell nuclear antigen (PCNA), showed an increased number of immunoreactive Leydig cells in the interstitium. In the flow cytometry analysis, proportions of diploid and tetraploid cells gradually decreased time-dependently until Day 28 after treatment, but showed an increase on Day 42, followed by a decrease on Day 70 after treatment. These data are strengthened by qualitative descriptions of lesions observed by histopathology. These results suggest that a high dose of 2-BP can decrease spermatogenesis by adversely affecting spermatogonia followed by depletion of spermatocytes, spermatids, and spermatozoa, with subsequent testicular atrophy. The atrophied testes may not regenerate completely. The number of Leydig cells may increase mildly with 10 weeks of recovery.

Testing the potential of sodium fluoride to affect spermatogenesis: a morphometric study

This study provides quantitative information on the effect of sodium fluoride (NaF) on the testes of F1 generation male rats exposed in utero and during lactation to NaF at one of four concentrations (25, 100, 175, 250 ppm). At weaning, the F1 generation males were exposed to NaF in their drinking water for 14 weeks, after which time testicular tissues were perfusion-fixed with glutaraldehyde and observed after being embedded in plastic. The seminiferous tubules comprised 89%, 87%, 88%, 88% and 88% of the total testis volume while the interstitial space occupied 9.3%, 11.2%, 10.2%, 9.8% and 9.9% of the total testis volume for the 0, 25, 100, 175 and 250 ppm NaF treatment groups, respectively. Statistically significant differences between control and NaF-treated rats were not observed with respect to absolute volume of the seminiferous tubules, interstitial space, Leydig cells, blood vessels boundary layer, lymphatic space, macrophages, tubular lumen or absolute tubular length and absolute tubular surface area, mean Sertoli cell nucleoli number per tubular cross-section, mean seminiferous tubule diameter and the mean height of the seminiferous epithelium. A statistically significant decrease in the absolute volume and volume percent of the lymphatic endothelium was observed in the 175 and 250 ppm NaF-treated groups and in the testicular capsule in the 100 ppm NaF-treated groups. The significance of this finding is unknown at the present time. Overall, the quantitative information obtained suggests that exposure to NaF at the doses used in the present study does not adversely affect testis structure or spermatogenesis in the rat.

The selective estrogen receptor modulator, raloxifene: reproductive assessments in adult male rats

Raloxifene HCl is a nonsteroidal, selective estrogen receptor modulator developed for postmenopausal osteoporosis. Reproductive toxicity of raloxifene was examined in adult male CD rats after the oral administration of doses of 0, 10, 30, or 100 mg/kg/d. In the first study, males (12/group) were treated for 2 weeks followed by 2 weeks without treatment. After dose administration on Day 13, 6 males/group were cohabited with untreated females (1:2) for up to 7 d. Males were killed on Day 14 or 28 (6/group each day). Sperm were collected from the right cauda epididymis and evaluated for relative concentration, motion characteristics, and breakage. The kinetics of spermatogenesis were examined by DNA flow cytometry. The left testis and epididymis were preserved for histopathologic evaluation. Females were examined for reproductive status on Gestation Day 13. In a second study, males (20/group) were treated for 7 weeks (4 weeks prior to cohabitation during a 2-week cohabitation period, and for 1 additional week). Treated males were cohabited with untreated females (1:1). On Gestation Day 20, untreated females were examined for reproductive status and fetuses were examined for viability, weight, gender, and morphology. At necropsy, male reproductive tissues were collected, weighed, and preserved for histopathologic evaluation. In both studies, male body weight gain and food consumption were depressed at all dose levels. There was no indication in either study that raloxifene caused important changes in sperm production, sperm quality, or male reproductive performance at doses as high as 100 mg/kg/d.

Adequacy of required regulatory hazard testing for the detection of potential hormonal activity of crop protection chemicals

The capacity of some synthetic chemicals, the so-called "endocrine-disrupting chemical," to alter hormonal activity, as well as the adequacy of the testing of chemicals to evaluate this capacity, has been called into question. Among the chemicals indicted have been certain crop protection agents or pesticides. Crop protection chemicals rank among the most closely regulated and thoroughly tested chemicals in use in both the human health and environmental hazard areas. However, it has been proposed that in vitro and in vivo screening tests be used to identify potential endocrine-active chemicals and to supplement or replace required regulatory bioassays. In vitro tests, such as receptor binding, examine a single chemical event, do not measure toxicity, post-receptor-mediated biological response, or the absorption, distribution, metabolism, and elimination of a chemical. Therefore, data derived solely from such a limited testing technique should not be used as a basis for selection of chemicals for making regulatory decisions. In vivo screening tests, such as the uterotrophic assay, which promise to provide a rapid answer to a targeted question, do not capture the complexity of the biological response. As in the case with in vitro tests, results from a single in vivo test, such as a change in uterine weight, should not be used as a basis for regulatory decision making. Further, it has been suggested that such a screening battery should be put into place for ecotoxicity testing. Yet it is well recognized that endocrine-active chemicals that affect fish and wildlife in their natural habitat have been shown to cause similar adverse effects in laboratory test animals. Therefore, these screening tests do not add value to the current regulatory test battery. Evidence is presented that demonstrates that the regulatory safety assessment paradigm has a low likelihood of missing potential endocrine-active chemicals and has served society well.

Flow cytometric evaluation of the effects of doxorubicin on rat spermatogenesis

Histopathologic examination of testicular tissue allows testicular impairment to be investigated. As an alternative to histopathology, flow cytometry (FCM) using a triple staining technique that combines DNA-ploidy with mitochondria stainability and vimentin immunostaining has also been utilized to evaluate testicular damage. In this article we evaluate the effects on spermatogenesis after acute exposure of rats to doxorubicin. Testicular cell suspensions of treated and control animals were analyzed by FCM. This allows several cell types to be identified and quantified, giving a control pattern. Deviations from this control pattern are considered as an indication of testicular damage. Doxorubicin produced a depletion of spermatogonia as early as 3 d after treatment. This effect could be followed through the temporal evolution of spermatogenesis. Comparable results were obtained by histopathology. The presented results show that FCM is a suitable and sensitive method for the detection of testicular damage. The advantages of FCM over other techniques include its rapidity and objectivity.

Evaluation of testicular toxicity in safety evaluation studies: the appropriate use of spermatogenic staging

Toxicology of the male reproductive system has received increased interest in recent years partly fuelled by the growing reports of falling sperm counts and rising reproductive disorders in the human population. Recently revised regulatory guidelines for the safety assessment of pharmaceuticals and chemicals on reproduction and fertility have emphasized the importance of detailed histopathological examination of the testes as a sensitive method for detecting disturbances in spermatogenesis. Unfortunately this has been accompanied by a general confusion regarding a practical approach to undertaking such a detailed examination, particularly in respect to the use of spermatogenic or tubular staging to identify subtle disturbances in spermatogenesis. The ability to identify tubular stages of the spermatogenic cycle in sections of testis plus a good understanding of the spermatogenic process and its dynamics are essential in order to carry out a sensitive of testicular histopathology and to interpret the changes seen. A rational approach is required initially to detect and subsequently to characterize toxic effects to the male reproductive system. It is important that a distinction is made between these two objectives since different study designs are required and different methodology may be employed to produce the type of information or data required.

Third international conference on harmonization of technical requirements for registration of pharmaceuticals for human use--a toxicologist's perspective

This overview provides a perspective on the ICH process and outcomes based on the third international conference held in Yokohama, Japan, in November/December 1995. It is an attempt to provide awareness of this process to the toxicologic pathology community from the point of view of a practicing toxicologist and meeting attendee and to consolidate much of the information on this process in one place. The ICH process is an active, and ongoing process to improve the standardization of safety assessment testing throughout the world, and further changes will no doubt have occurred by the time this document is published.