Neonatal polychlorinated biphenyl treatment increases adult testis size and sperm production in the rat

Exogenous taurine administration abates reproductive dysfunction in male rats exposed to silver nanoparticles

The broad contemporary applications of silver nanoparticles (AgNPs) have been associated with various toxicities including reproductive toxicity. Taurine is well acknowledged for its potent pharmacological role in numerous disease models and chemically-mediated toxicity. We investigated the effect of taurine on AgNPs-induced reproductive toxicity in male rats. The animals were intraperitoneally injected with AgNPs (200 μg/kg) alone or co-administered with taurine at 50 and 100 mg/kg for 21 successive days. Exogenous taurine administration significantly abated AgNPs-induced oxidative injury by decreasing the levels of oxidative stress indices while boosting antioxidant enzymes activities and glutathione level in the hypothalamus, testes and epididymis of exposed animals. Taurine administration alleviated AgNPs-induced inflammatory response and caspase-3 activity, an apoptotic biomarker. Moreover, taurine significantly improved spermiogram, reproductive hormones and the marker enzymes of testicular function in AgNPs-treated animals. The ameliorative effect of taurine on pathological lesions induced by AgNPs in the exposed animals was substantiated by histopathological data. This study provides the first mechanistic evidence that taurine supplementation affords therapeutic effect against reproductive dysfunction associated with AgNPs exposure in male rats.

Enhanced sperm production in bulls following transient induction of hypothyroidism during prepubertal development

Male reproductive capacity is a critical component of cattle production and the majority of genetic gain is made via selective utilization of gametes from desirable sires. Thus, strategies that enhance sperm production increase the availability of elite genetics for use in improving production characteristics of populations on a worldwide scale. In all mammals, the amount of sperm produced is strongly correlated to the number of Sertoli cells in testes. Studies with rodents showed that the size of the Sertoli cell population is set during prepubertal development via signaling from thyroid hormones. Here, we devised a strategy to increase Sertoli cell number in bulls via induction of a transient hypothyroidic state just prior to and extending beyond the period of Sertoli cell proliferation that we found to normally cease between 4.5 and 5 mo of age. In adulthood, these bulls produced a significantly greater number of sperm compared to age-matched controls and their testes contained nearly 2 times more Sertoli cells. Importantly, sperm motility, morphology, fertilizing ability, and viability after cryopreservation were found to be no different for treated bulls compared to untreated control bulls. This strategy of transient induction of hypothyroidism during a defined period of prepubertal development in bulls could prove to be an efficacious approach for enhancing daily sperm production in genetically desirable sires that will, in turn, provide an avenue for improving the efficiency of commercial cattle production.

Molecular Mechanisms and Signaling Pathways Involved in Sertoli Cell Proliferation

Sertoli cells are somatic cells present in seminiferous tubules which have essential roles in regulating spermatogenesis. Considering that each Sertoli cell is able to support a limited number of germ cells, the final number of Sertoli cells reached during the proliferative period determines sperm production capacity. Only immature Sertoli cells, which have not established the blood-testis barrier, proliferate. A number of hormonal cues regulate Sertoli cell proliferation. Among them, FSH, the insulin family of growth factors, activin, and cytokines action must be highlighted. It has been demonstrated that cAMP/PKA, ERK1/2, PI3K/Akt, and mTORC1/p70SK6 pathways are the main signal transduction pathways involved in Sertoli cell proliferation. Additionally, c-Myc and hypoxia inducible factor are transcription factors which participate in the induction by FSH of various genes of relevance in cell cycle progression. Cessation of proliferation is a pre-requisite to Sertoli cell maturation accompanied by the establishment of the blood-testis barrier. With respect to this barrier, the participation of androgens, estrogens, thyroid hormones, retinoic acid and opioids has been reported. Additionally, two central enzymes that are involved in sensing cell energy status have been associated with the suppression of Sertoli cell proliferation, namely AMPK and Sirtuin 1 (SIRT1). Among the molecular mechanisms involved in the cessation of proliferation and in the maturation of Sertoli cells, it is worth mentioning the up-regulation of the cell cycle inhibitors p21Cip1, p27Kip, and p19INK4, and of the gap junction protein connexin 43. A decrease in Sertoli cell proliferation due to administration of certain therapeutic drugs and exposure to xenobiotic agents before puberty has been experimentally demonstrated. This review focuses on the hormones, locally produced factors, signal transduction pathways, and molecular mechanisms controlling Sertoli cell proliferation and maturation. The comprehension of how the final number of Sertoli cells in adulthood is established constitutes a pre-requisite to understand the underlying causes responsible for the progressive decrease in sperm production that has been observed during the last 50 years in humans.

Chlorinated biphenyls effect on estrogen-related receptor expression, steroid secretion, mitochondria ultrastructure but not on mitochondrial membrane potential in Leydig cells

To characterize polychlorinated biphenyls (PCBs) action on Leydig cells, PCBs congeners, low-chlorinated (delor 103; d103) and high-chlorinated ones (delor 106; d106) were selected. The cells were treated according to PCBs dose (d103 or d106 0.2 ng/ml in low doses:, or 2 ng/ml in high doses) and type (d103 + d106 in low doses or 103 + 106 in high doses). After 24 h treatment with PCBs, a distinct increase in estrogen-related receptors (ERRs type α, β and γ) expression was revealed. However, the dose- and type-dependent PCBs effect was mostly exerted on ERRα expression. A similar increase in ERRs expression was demonstrated by estradiol but not testosterone, which was without an effect on ERRs. PCBs caused no decrease in the membrane potential status of Leydig cells (either in dose or type schedule) but had severe effects on the mitochondria number and structure. Moreover, PCBs markedly increased calcium (Ca2+) concentration and sex steroid secretion (both androgens and estrogens were elevated). These findings suggest a similar estrogenic action of PCBs congeners (d103 and d106) on Leydig cell function. We report dose- and type-specific effects of PCBs only on Leydig cell ERRs expression. Both delors showed common effects on the mitochondria ultrastructural and functional status. Based on our results, ERRα seems to be the most sensitive to hormonal modulation. The increases in Ca2+ and sex steroid secretion may be due to the activation of ERRs by PCBs binding and/or direct effect of PCBs on ERRs mRNA/protein expression. Nevertheless, to confirm the existence of possible relationships between ERRs signaling (including PCBs as ligands) and mitochondria function in Leydig cells, further intensive studies are needed.

Suppression of the brain-pituitary-testicular axis function following acute arsenic and manganese co-exposure and withdrawal in rats

Despite the fact that most environmental exposures to metals do not occur in isolation, the combined effects of metal mixtures on brain-pituitary-gonadal axis are poorly known. The present study investigated the impacts of co-exposure to arsenic (As) and manganese (Mn) on sperm characteristics, reproductive hormones and selected oxidative stress indices in the brain, testes and epididymis of rats following exposure for 15 consecutive days to 60mg/L of AsO₂Na and 30mg/L of MnCl₂ in drinking water. The results showed that while the brain weight remained unaffected, the fluid intake and the weights of testes and epididymis significantly (p<0.05) decreased in all the treatment groups. A significant decrease in the body weight gain when compared with control was noted only in the co-exposed rats. Moreover, the significant decreases in the antioxidant status in brain, testes and epididymis as well as in the circulatory concentrations of follicle-stimulating hormone, luteinizing hormone and testosterone were similar following separate or combined exposure of rats to As and Mn. The marked oxidative damage in the investigated tissues was accompanied by a significant decrease in the sperm quantity and quality in all the treated rats when compared with the control. Interestingly, most of the parameters determined immediately after the exposure period persisted in rats from the withdrawal experiment. Collectively, co-exposure to As and Mn suppressed the brain-pituitary-testicular axis function and the post-testicular events such as sperm function possibly via a mechanism involving persistent oxidative stress and endocrine disruption in the exposed rats.

The biological fate of decabromodiphenyl ethane following oral, dermal or intravenous administration

1. It was important to investigate the disposition of decabromodiphenyl ethane (DBDPE) based on concerns over its structural similarities to decabromodiphenyl ether (decaBDE), high potential for environmental persistence and bioaccumulation, and high production volume. 2. In the present study, female Sprague Dawley rats were administered a single dose of [¹⁴C]-DBDPE by oral, topical or IV routes. Another set of rats were administered 10 daily oral doses of [¹⁴C]-DBDPE. Male B6C3F1/Tac mice were administered a single oral dose. 3. DBDPE was poorly absorbed following oral dosing, with 95% of administered [¹⁴C]-radioactivity recovered in the feces unchanged, 1% recovered in the urine and less than 3% in the tissues at 72 h. DBDPE excretion was similar in male mice and female rats. Accumulation of [¹⁴C]-DBDPE was observed in liver and the adrenal gland after 10 daily oral doses to rats. 4. Rat and human skin were used to assess potential dermal uptake of DBDPE. The dermis was a depot for dermally applied DBDPE; conservative estimates predict ∼14 ± 8% of DBDPE may be absorbed into human skin in vivo; ∼7 ± 4% of the parent chemical is expected to reach systemic circulation following continuous exposure (24 h). 5. Following intravenous administration, ∼70% of the dose remained in tissues after 72 h, with the highest concentrations found in lung (1223 ± 723 pmol-eq/g), spleen (1096 ± 369 pmol-eq/g) and liver (366 ± 98 pmol-eq/g); 5 ± 1% of the dose was recovered in urine and 26 ± 4% in the feces.

Impact of polychlorinated biphenyl Aroclor 1254 on testicular antioxidant system in adult rats

To clarify the reproductive toxicity of polychlorinated biphenyl compounds through determination of testicular lipid peroxidation, reactive oxygen species and enzymatic and non-enzymatic antioxidants in rats exposed to Aroclor 1254. Adult male rats were administered Aroclor 1254 at a dose of 2 mg/kg per day ip for 30 days. The rats were sacrificed 24 hours after last dosing and the serum and other tissues collected and processed for relevant determinations. The body weight and the weights of the testis, epididymis, ventral prostate and seminal vesicle and the serum testosterone and estradiol were significantly decreased in Aroclor 1254 treated rats. The testicular lipid peroxidation, hydrogen peroxide and hydroxyl radical were significantly elevated whereas, testicular antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione-S-transferase (GST) and glutathione reductase (GR) were significantly decreased. The non-enzymatic antioxidants, vitamin C and vitamin E, were also decreased. These results suggest that Aroclor 1254 induces an increase in the lipid peroxidation, hydrogen peroxide and hydroxyl radical and diminish in the antioxidant defense system in rats, indicating that the free radical-dependent mechanism may play an important role in the testicular toxicity of polychlorinated biphenyls.

Quercetin ameliorates polychlorinated biphenyls-induced testicular DNA damage in rats

Polychlorinated biphenyls (PCBs) are a group of environmental contaminants widely reported to cause gonadal toxicity in both humans and animals. This study investigated the amelioratory role of quercetin in PCBs-induced DNA damage in male Wistar rats. Polychlorinated biphenyls were administered intraperitoneally at a dose of 2 mg kg(-1) alone or in combination with quercetin (orally) at 50 mg kg(-1) for 25 days. Quercetin modulation of PCBs-induced gonadal toxicity was evaluated using selected oxidative stress indices, comet assay, measurement of DNA concentration and histology of the testes. Administration of PCBs alone caused a significant (P < 0.05) depletion in the total thiol level in testes of treated rats. Conversely, the levels of reactive oxygen species (ROS) and thiobarbituric acid reactive substances (TBARS) production were markedly elevated in testes of PCBs-treated rats compared with control. Further, PCBs exposure produced statistically significant increases in DNA tail migration, degraded double-stranded DNA (dsDNA) concentration and histological alterations of testes of the treated rats compared to control. Quercetin cotreatment significantly improved the testicular antioxidant status, decreased DNA fragmentation and restored the testicular histology, thus demonstrating the protective effect of quercetin in PCBs-treated rats.

Dose-dependent effects of perinatal hypothyroidism on postnatal testicular development in rat offspring

The role of thyroid hormones in gonad development remains incompletely understood. We examined the dose-related effects of perinatal hypothyroidism induced by a reversible goitrogen, 6-propyl-2-thiouracil (PTU), on reproductive development in male rat offspring. Timed-pregnant Sprague-Dawley rats were orally administered PTU (0, 0.5, 1.0, or 2.0 mg/kg/day) by gavage from gestational day 15 through postnatal day 20. We observed a significant dose-dependent decrease in body weight in offspring with PTU exposure up to 13 weeks of age, but body weight became comparable among groups by 26 weeks of age. Testicular weight tended to be lower up to 7 weeks but was higher after 13 weeks of age. Epididymis weight was not different among the groups at any age. Plasma concentrations of thyroxine and triiodothyronine in the PTU groups were significantly lower at 3 weeks of age but recovered to normal levels by 26 weeks of age. No dose-related trend in plasma testosterone concentrations was found. Seminiferous tubules were larger at 13 and 26 weeks of age with PTU exposure. The number of Sertoli cells was significantly higher from 3 through 26 weeks of age. The number of Leydig cells was significantly lower up to 7 weeks of age but was comparable among groups from 13 weeks of age onwards. Thus, transient gestational and lactational thyroid hormone suppression induced small testes in early life but led to paradoxical dose-dependent testicular enlargement in adults as indicated partly by larger seminiferous tubules with numerous Sertoli cells in male rat offspring.

Association between chemical pattern in breast milk and congenital cryptorchidism: modelling of complex human exposures

During the past four decades, there has been an increase in the incidence rate of male reproductive disorders in some, but not all, Western countries. The observed increase in the prevalence of male reproductive disorders is suspected to be ascribable to environmental factors as the increase has been too rapid to be explained by genetics alone. To study the association between complex chemical exposures of humans and congenital cryptorchidism, the most common malformation of the male genitalia, we measured 121 environmental chemicals with suspected or known endocrine disrupting properties in 130 breast milk samples from Danish and Finnish mothers. Half the newborns were healthy controls, whereas the other half was boys with congenital cryptorchidism. The measured chemicals included polychlorinated biphenyls (PCBs), polybrominated diphenyl-ethers, dioxins (OCDD/PCDFs), phthalates, polybrominated biphenyls and organochlorine pesticides. Computational analysis of the data was performed using logistic regression and three multivariate machine learning classifiers. Furthermore, we performed systems biology analysis to explore the chemical influence on a molecular level. After correction for multiple testing, exposure to nine chemicals was significantly different between the cases and controls in the Danish cohort, but not in the Finnish cohort. The multivariate analysis indicated that Danish samples exhibited a stronger correlation between chemical exposure patterns in breast milk and cryptorchidism than Finnish samples. Moreover, PCBs were indicated as having a protective effect within the Danish cohort, which was supported by molecular data recovered through systems biology. Our results lend further support to the hypothesis that the mixture of environmental chemicals may contribute to observed adverse trends in male reproductive health.

Dioxin and polychlorinated biphenyl concentrations in mother's serum and the timing of pubertal onset in sons

BACKGROUND

Animal studies have demonstrated that timing of pubertal onset can be altered by prenatal exposure to dioxins or polychlorinated biphenyls (PCBs), but studies of human populations have been quite limited.

METHODS

We assessed the association between maternal serum concentrations of dioxins and PCBs and the sons' age of pubertal onset in a prospective cohort of 489 mother-son pairs from Chapaevsk, Russia, a town contaminated with these chemicals during past industrial activity. The boys were recruited at ages 8 to 9 years, and 4 years of annual follow-up data were included in the analysis. Serum samples were collected at enrollment from both mothers and sons for measurement of dioxin and PCB concentrations using high-resolution mass spectrometry. The sons' pubertal onset--defined as pubertal stage 2 or higher for genitalia (G) or pubic hair (P), or testicular volume >3 mL--was assessed annually by the same physician.

RESULTS

In multivariate Cox models, elevated maternal serum PCBs were associated with earlier pubertal onset defined by stage G2 or higher (4th quartile hazard ratio = 1.7 [95% confidence interval = 1.1- 2.5]), but not for stage P2 or higher or for testicular volume >3 mL. Maternal serum concentrations of dioxin toxic equivalents were not consistently associated with the sons' pubertal onset, although a dose-related delay in pubertal onset (only for G2 or higher) was seen among boys who breast-fed for 6 months or more.

CONCLUSIONS

Maternal PCB serum concentrations measured 8 or 9 years after sons' births--which may reflect sons' prenatal and early-life exposures--were associated with acceleration in some, but not all, measures of pubertal onset.

Diet exposure to technical hexabromocyclododecane (HBCD) affects testes and circulating testosterone and thyroxine levels in American kestrels (Falco sparverius)

Hexabromocyclododecane (HBCD) is a high-production-volume, brominated flame-retardant that is used in items such as polystyrene foams. HBCD has been detected in the environment, wildlife tissues and in humans globally with some of the highest recorded levels in predatory birds. This study examined the effects of exposure to environmentally relevant levels of HBCD on the reproductive physiology of captive male American kestrels (Falco sparverius), a predatory bird. Two sets of males were used: one group not housed with females (unpaired: nc=12, nHBCD=10) and the second group housed with females (breeding: nc=10, nHBCD=20). All treatment birds were exposed to 0.51 μg HBCD/g kestrel/day technical HBCD, and controls to safflower oil only, injected into their food during seasonal testicular development. Unpaired males were exposed for 3 weeks and euthanized for testicular analysis. Breeding males were exposed for 3 weeks prior to pairing and throughout the courtship period. The HBCD-exposed unpaired males had heavier testes (p≤0.017) and a trend towards more seminiferous tubules containing elongated spermatids (p=0.052). There was also a moderate increase in plasma testosterone concentrations (p=0.056) compared to controls. In breeding males, testosterone levels increased during courtship to culminate in higher levels than controls by the time the first egg was laid (p=0.010) and circulating free and total T4 was reduced throughout. The number of sperm cells reaching the perivitelline layer of the first egg for breeding males did not differ between the two groups. This study is the first report that HBCD exposure at environmentally relevant levels alters reproductive physiology in male birds and suggests that birds may be more sensitive to HBCD than mammals.

Time-of-flight secondary ion mass spectrometry imaging demonstrates the specific localization of deca-bromo-diphenyl-ether residues in the ovaries and adrenal glands of exposed rats

Deca-bromo-diphenyl ether (DBDE) is one of the most efficient brominated flame retardant (BFR) available on the market. We recently demonstrated that when administered to female rat by oral route, DBDE is efficiently absorbed, with the highest residual concentrations found in two endocrine glands, namely the adrenal glands and the ovaries. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) imaging, a technique usually used for the study of endogenous compounds, was applied for the first time to a persistent organic pollutant, allowing to detect and to precisely localize DBDE residues in these two target tissues. The detection of the bromide ion ((81)Br isotope) by TOF-SIMS mass spectrometry imaging allowed us to demonstrate a marked cortical tropism of DBDE residues for the adrenal glands in female rats dosed per os 2 mg·kg(-1) DBDE, daily, over 96 h. In ovaries, DBDE residues were found to be concentrated in spots corresponding to part of the corpora lutea. Hepatic residues of DBDE were found to be homogeneously distributed. Due to the intrinsic toxicity of DBDE, its accumulation in the adrenal glands and the ovaries may be connected to the mechanisms of actions by which DBDE could trigger endocrine disruption in mammals.

Parenteral paradichlorobenzene exposure reduces sperm production, alters sperm morphology and exhibits an androgenic effect in rats and mice

Rats and mice (8 animals per species per group) were injected subcutaneously or intraperitoneally with paradichlorobenzene (PDCB) at doses of 0, 100, 200 and 400 mg/kg/day, 4-5 days a week, for 8 weeks (for rats) and either 2 or 6 weeks (for mice). Prostate and seminal vesicle weights were significantly increased in PDCB-treated rats but not in mice. Major histopathologic injuries were not found in testis and epididymis of both species. Daily sperm production was depressed in both species in a dose-response manner. Serum testosterone levels were not significantly changed in both species. Sperm morphology was evaluated in rats intraperitoneally administered PDCB at a dose of 800 mg/kg. Abnormal sperms with reduced hook, bent neck, coiled flagellum, bent flagellum and bent flagellum tip were significantly increased in treated rats. In Hershberger assay, PDCB administration increased weights of ventral prostate gland, seminal vesicle, levator ani/bulbocavernosus muscle and glans penis in castrated rats, and also weights of ventral prostate gland and glans penis in castrated mice. PDCB and 2,5-dichlorophenol (the major metabolite) did not bind androgen receptor (AR) up to 10 mM. In conclusion, PDCB affects sperm production and morphology but is somewhat androgenic independently from AR binding in rats and mice.

Differential effects of polychlorinated biphenyl congeners on serum thyroid hormone levels in rats

Polychlorinated biphenyls (PCBs) are known to reduce serum thyroxine (T(4)) in rats, but the relative effects of individual PCB congeners on thyroid hormones are not known. Thus, male Sprague-Dawley rats were administered Aroclor 1254, Aroclor 1242 (4, 8, 16, or 32 mg/kg/day), PCB 95 (2,2',3,5',6-pentachlorobiphenyl), PCB 99 (2,2',4,4',5-pentachlorobiphenyl), PCB 118 (2,3',4,4',5-pentachlorobiphenyl) (2, 4, 8, or 16 mg/kg/day), PCB 126 (3,3'4,4',5-pentachlorobiphenyl) (2.5, 5, 10, 20, or 40 microg/kg/day), TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) (0.14, 0.43, 1.3, or 3.9 microg/kg/day), or corn oil via oral gavage for 7 days. Rats were necropsied 24 h after the last dose. Serum thyroid hormone levels were evaluated by radioimmunoassay, and induction of hepatic Cyp1a (a TCDD-inducible protein) and Cyp2b (a phenobarbital [PB]-inducible protein) activity was determined by ethoxyresorufin-O-deethylase and pentoxyresorufin-O-deethylase assays, respectively. Significant increases in Cyp1a activity occurred in response to PCBs, except PCB 95 and PCB 99. Aroclor 1254, PCB 99, and PCB 118 significantly induced Cyp2b activity. Serum total T(4) and free T(4) were dramatically reduced in response to each of the seven treatments in a dose-dependent manner. The marked T(4) reductions occurred in response to Aroclor 1254, PCB 99 (a PB-type congener), and PCB 118 (a mixed-type congener). In contrast, reductions in serum triiodothyronine (total and free) were variable and mild, and serum thyroid-stimulating hormone was not significantly affected by any of the compounds. These data indicate that the PB and mixed-type PCB congeners are more effective than the TCDD-type PCB congeners at reducing serum T(4).

Developmental exposure to pentachlorophenol affects the expression of thyroid hormone receptor beta1 and synapsin I in brain, resulting in thyroid function vulnerability in rats

Pentachlorophenol (PCP), a component of biocides and a contaminant in diverse tissue samples from humans from various geographic areas, disrupts regulatory effects of thyroid hormones. Here we examined the effects of developmental exposure of rats to PCP on various aspects of brain development, male reproductive function, and adrenal function, all of which are under thyroid hormones regulation. PCP was administered to dams and their offspring via drinking water (6.6 mg l(-1)) during gestation and lactation. Tissue samples were obtained from dams, 3-week-old weanling pups, and 12-week-old pups. Gene expressions of thyroid hormone receptor beta1 and synapsin I, factors that promote brain growth, was increased in the cerebral cortex of PCP-treated weanling females, whereas plasma concentrations of total thyroxine were decreased in dams and weanling pups, and plasma thyroid-stimulating hormone concentrations were higher in PCP-treated weanling males. PCP caused a decrease in plasma corticosterone concentrations in 12-week-old female rats, but not in male rats or weanling females. PCP-treated male pups had significantly increased testis weight at 12 week of age. No overt signs of toxicity were noted throughout this study. Our results show that PCP exposure during development causes thyroid function vulnerability, testicular hypertrophy in adults, and aberrations of brain gene expression.

Effects of vitamins C and E on steroidogenic enzymes mRNA expression in polychlorinated biphenyl (Aroclor 1254) exposed adult rat Leydig cells

Polychlorinated biphenyls (PCBs) are ubiquitous and persistent environmental contaminants that disturb normal endocrine functions including gonadal functions in humans and mammals. The present study was conducted to elucidate the protective role of vitamins C and E against Aroclor 1254-induced changes in Leydig cell steroidogenic acute regulatory (StAR) protein and steroidogenic enzymes mRNA expression. Adult male rats were dosed for 30 days with daily intraperitoneal (i.p.) injection of 2 mg/kg Aroclor 1254 or vehicle (corn oil). One group of rats was treated with vitamin C (100 mg/kg bw day) while the other group was treated with vitamin E (50 mg/kg bw day) orally, simultaneously with Aroclor 1254 for 30 days. One day after the last treatment, animals were euthanized and blood was collected for the assay of serum hormones such as luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone and estradiol. The serum androgen binding protein was also estimated. Testes were quickly removed and Leydig cells were isolated in aseptic condition. Purity of Leydig cells was determined by 3beta-hydroxysteroid dehydrogenase (3beta-HSD) staining methods. Purified Leydig cells were used for quantification of androgen and estrogen receptors. In addition, total RNA was isolated from control and treated Leydig cells to monitor the steady-state mRNA levels by RT-PCR for StAR protein, cytochrome P(450)scc, 3beta-HSD and 17beta-HSD. Aroclor 1254 treatment significantly reduced the serum LH, FSH, testosterone, estradiol and androgen binding protein. In addition to this, Leydig cell androgen and estrogen receptors were markedly decreased. RT-PCR analysis of StAR mRNA level did not alter Aroclor 1254 treatment while steroidogenic enzymes such as cytochrome P(450)scc, 3beta-HSD and 17beta-HSD mRNAs were drastically decreased in Aroclor 1254 treatment. However, the simultaneous administration of vitamins C or E in Aroclor 1254-exposed rats resulted a significant restoration of all the above-mentioned parameters to the control level. These observations suggest that vitamins C and E have ameliorative role against PCBs-induced testicular Leydig cells dysfunction.

Studies on the protective role of vitamin C and E against polychlorinated biphenyl (Aroclor 1254)--induced oxidative damage in Leydig cells

Free radical production and lipid peroxidation are potentially important mediators in testicular physiology and toxicology. Polychlorinated biphenyls (PCBs) are global environmental contaminants that cause disruption of the endocrine system in human and animals. The present study was conducted to elucidate the protective role of vitamin C and E against Aroclor 1254-induced changes in Leydig cell steroidogenesis and antioxidant system. Adult male rats were dosed for 30 days with daily intraperitoneal (ip) injection of 2 mg/kg Aroclor or vehicle (corn oil). One group of rats was treated with vitamin C (100 mg/kg bw/day) while the other group was treated with vitamin E (50 mg/kg bw/day) orally, simultaneously with Aroclor 1254 for 30 days. One day after the last treatment, animals were euthanized and blood was collected for the assay of serum hormones such as luteinizing hormone (LH), thyroid stimulating hormone (TSH), prolactin (PRL), triiodothyronine (T(3)), thyroxine (T(4)), testosterone and estradiol. Testes were quickly removed and Leydig cells were isolated in aseptic condition. Purity of Leydig cells was determined by 3beta-hydroxysteroid dehydrogenase (3beta-HSD) staining method. Purified Leydig cells were used for quantification of cell surface LH receptors and steroidogenic enzymes such as cytochrome P(450) side chain cleavage enzyme (P(450)scc), 3beta-hydroxysteroid dehydrogenase (3beta-HSD) and 17beta-hydroxysteroid dehydrogenase (17beta- HSD). Leydig cellular enzymatic antioxidants superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), gamma-glutamyl transpeptidase (gamma-GT), glutathione-S-transferase (GST) and non-enzymatic antioxidants such as vitamin C and E were assayed. Lipid peroxidation (LPO) and reactive oxygen species (ROS) were also estimated in Leydig cells. Aroclor 1254 treatment significantly reduced the serum LH, TSH, PRL, T(3), T(4), testosterone and estradiol. In addition to this, Leydig cell surface LH receptors, activities of the steroidogenic enzymes such as cytochrome P(450)scc, 3beta-HSD, 17beta-HSD, antioxidant enzymes SOD, CAT, GPX, GR, gamma-GT, GST and non-enzymatic antioxidants such as vitamin C and E were significantly diminished whereas, LPO and ROS were markedly elevated. However, the simultaneous administration of vitamin C and E in Aroclor 1254 exposed rats resulted a significant restoration of all the above-mentioned parameters to the control level. These observations suggest that vitamin C and E have ameliorative role against adverse effects of PCB on Leydig cell steroidogenesis.

Endocrine disruption induced by organochlorines (OCs): field studies and experimental models

Long-range transport of persistent organic compounds by air and ocean currents from industrialized areas resulted in high levels of these pollutants in food webs in the Svalbard area. With the aim to test if organochlorine (OC) exposure in free-living polar bears from Svalbard affected their plasma steroid hormone concentrations, it was found that polychlorinated biphenyls (PCBs) were associated with increased progesterone levels in females. The sum of pesticides (sigma pesticides) and sigma PCBs contributed significantly negative to the variation of the plasma testosterone in males, and the overall contribution of the OCs to the plasma cortisol variation was negative. A second objective was to study the effects of selected OCs (i.e., PCB 153 and PCB 126) on animal health as a consequence of effects on endocrine-regulated functions such as reproduction and immunity in a goat model focusing on long-term and low-level exposure during the periods of fetal development and in the neonatal period. Additionally, acute exposure was studied in adult mice. The results indicated that exposure to low doses of PCB 153 in utero and in the suckling period influenced reproductive functions and both PCB 153 and PCB 126 exerted immunomodulatory effects on the offspring, whereas acute exposure of adult mice had minor effects on male reproductive function.

Effects of single non-ortho, mono-ortho, and di-ortho chlorinated biphenyls on human sperm functions in vitro

Polychlorinated biphenyls (PCBs) are ubiquitous pollutants in the environment. They are present in body fluids associated with reproduction such as follicular fluid, seminal fluid and cervical mucus. Most PCB effects are mediated through the aryl hydrocarbon receptor, which is present in human spermatozoa. Additionally, PCBs may alter various biochemical reactions, such as calcium homeostasis. Therefore we investigated the effects of single non-ortho PCB 126, mono-ortho PCB 118, and di-ortho PCB 153 on human sperm motility, vitality, and calcium-dependent acrosome reaction (AR) in vitro. Human spermatozoa were either treated with different single PCB congeners or their combinations for 5 h at 37 degrees C (spontaneous AR), or for 16 h at room temperature and 4 degrees C (induced AR). Motility was measured after 5 h of incubation. Compared with the controls, PCB exposure had no effects on the percentage of living acrosome reacted spermatozoa, vitality, and motility. There was no difference in the inducibility of the AR between treatment groups and the respective controls after long term incubation. The PCB concentrations used were far higher than those found in cervical mucus or seminal fluid. In vivo effects of PCB congeners on human ejaculated spermatozoa seem to be unlikely. However these results cannot be easily transferred to the in vivo situation, because individual susceptibility has to be considered, and there is no information about synergistic or additive effects with other chemicals present in the male and female reproductive tract.

In Utero and Lactational Exposure to an Environmentally Relevant Organochlorine Mixture Disrupts Reproductive Development and Function in Male Rats1

We hypothesized that in utero and lactational exposure of male rats to a mixture of more than 15 organochlorines, resembling that found in blubber from northern Quebec seals, alters reproductive development and function. Female rats were gavaged with either corn oil (controls) or the organochlorine mixture in increasing doses (low, medium, and high) for 5 wk before mating and through gestation. Developmental effects were monitored in the male offspring from Postnatal Day (PND) 2 until PND 90. The high-dose mixture reduced the number of pups per litter, percentage of live offspring, and pup weights (P < 0.05). Because only three rats from the high-dose treatment survived, data from this group beyond PND 2 were not included in the statistical analyses. As assessed by the time of preputial separation, puberty was delayed in the pups from treated dams (P < 0.05). Testes weights in the medium-dose group were greater than those in controls on PND 21 (P < 0.05). Ventral prostate weights were lower for the medium-dose group on PND 60 (P < 0.05). On PND 90, weights of the epididymis, ventral prostate, and seminal vesicle of the medium-dose rats were reduced compared to those of controls (P < 0.05). On PND 90, sperm motility parameters assessed by computer-assisted sperm analysis were altered in the low- and medium-dose groups (P < 0.05). Testicular and epididymal morphology was severely affected in rats exposed to the high dose of the mixture. Serum testosterone, LH, FSH, prolactin, and total thyroxine levels did not differ because of organochlorine treatment. Therefore, in utero and lactational exposure to an environmentally relevant organochlorine mixture adversely affects the reproductive system of male rats, perhaps via antiandrogenic effects during testis development, suggesting a possible reproductive health hazard for humans and other species.

Effect of Aroclor 1254 on Sertoli cellular antioxidant system, androgen binding protein and lactate in adult rat in vitro

Polychlorinated biphenyls (PCBs) are persistent and bioaccumulative environmental toxicants. Previous studies suggested that PCBs (Aroclor 1254) induce toxic effects including reproductive toxicity. The present study was designed to investigate the impact of Aroclor 1254 on Sertoli cellular function and antioxidant system of adult rat in vitro. Sertoli cells were isolated from adult rat testes and treated with various concentrations (10(-10) to 10(-7) M) of Aroclor 1254 for 6, 12 and 24 h. After the treatment period, cell viability was assessed and the Sertoli cellular antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), gamma-glutamyl transpeptidase (gamma-GT) and glutathione reductase (GR) and lipid peroxidation (LPO) were assayed. In addition, androgen binding protein (ABP) and lactate secretions were also quantified in Sertoli cell culture medium. Sertoli cellular viability and activity of antioxidant enzymes were significantly reduced in Aroclor 1254 (10(-10) to 10(-7) M) treatment for 6, 12 and 24 h whereas, the Sertoli cellular lipid peroxidation was significantly increased in a dose and duration dependent manner. In addition, ABP secretion diminished and lactate secretion was significantly elevated in the same manner. To conclude, the present study suggested that Aroclor 1254 disrupts Sertoli cellular metabolic functions such as ABP, lactate secretions and activity of antioxidant enzymes.

In utero and lactational exposure of Long-Evans rats to ammonium perchlorate (AP) disrupts ovarian follicle maturation

Ammonium perchlorate (AP) is a powerful oxidizer manufactured almost exclusively for the aerospace industry. AP salts are also used in airbags, flares, fertilizers, enamels and paints. As a result of widespread industrial use, AP has become a persistent environmental contaminant of drinking water in several U.S. states. AP ion disrupts the trapping of iodide as well as facilitates the discharge of unorganified iodide from the thyroid gland. Such disturbances in thyroid hormone concentrations during critical periods of development are then known to cause profound reproductive and developmental defects, since thyroid hormones modulate both follicular development and steroidogenesis and affect estrogen metabolism and receptor. This study was designed (1) to determine whether exposure to a low or high concentration of AP (LAP, HAP) exerts detrimental effects on follicle maturation in the Long-Evans hooded rat and (2) to determine whether the modulatory effects of AP can be ameliorated by levo-thyroxine sodium (T4) supplementation. Animals were treated via deionized drinking water on GD 7-21 with LAP (0.4 mg/kg/day) or HAP (4.0 mg/kg/day). Half of each group was also given T4 supplements via drinking water on GD 7-21. Female pups were sacrificed on postnatal days 24/25, and the ovaries were excised, fixed for histology and analyzed. The analysis included a count, measurement and classification of preantral and antral follicles in the greatest cross-sectional area of the ovary. The results indicated that treatment with the HAP significantly reduced the number of preantral follicles <50,000 microm2 and the total number of antral follicles in the <50,000, 50-100,000 and >100,000 microm2 size classes. In ovaries treated with the LAP, we observed no significant decrease in preantral follicles of any size class and only a significant reduction in the largest antral follicles. T4 only circumvented the effect on the number of small preantral and antral follicles; however, a significant diminution in the antral follicle number persisted in the mid-sized (HAP) and large (LAP, HAP)-sized classes. These data support the hypothesis that AP reduces the number of preantral and antral follicles in certain size classes in rats exposed during a critical period of development, and that T4 can attenuate the effects of AP on small preantral and antral follicles, but not on medium or large antral follicles. (T35ES007292 & ES08342.).

The inhibitory effects of polychlorinated biphenyl Aroclor 1254 on Leydig cell LH receptors, steroidogenic enzymes and antioxidant enzymes in adult rats

Polychlorinated biphenyls (PCBs) are global pollutants of major concern to human and animal reproductive health. The present study has examined the impact of Aroclor 1254 exposure on oxidative stress and testicular Leydig cell function. Adult albino male rats of the Wistar strain were dosed for 30 days with daily intraperitoneal injections of 2 mg/kg Aroclor 1254 or vehicle (corn oil). One day after the last treatment, animals were euthanized and blood collected for the assay of serum testosterone and estradiol. Testes were removed and Leydig cells were isolated for the assay of luteinizing hormone (LH) receptors, steroidogenic enzymes cytochrome P450 side chain cleavage enzyme (P450 scc), 3beta-hydroxysteroid dehydrogenase (3beta-HSD) and 17beta-hydroxysteroid dehydrogenase (17beta-HSD). Cellular antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR), and glutathione-S-transferase (GST) were also assayed. Lipid peroxidation (LPO) and reactive oxygen species (ROS) were quantified. Results showed that Aroclor 1254 exposure lowered serum testosterone and estradiol levels. Leydig cell LH receptor density, activities of the steroidogenic enzymes P450 scc, 3beta-HSD, 17beta-HSD, antioxidant enzymes SOD, CAT, GPX, GR, and GST were significantly diminished whereas, LPO and ROS significantly elevated. Taken together, these results suggest that inefficient LH receptors, steroidogenic enzymes and antioxidant enzymes are possible mechanisms by which Aroclor 1254 treatment disrupts Leydig cell steroidogenesis.

Effects of gestational and lactational exposure to low doses of PCBs 126 and 153 on anterior pituitary and gonadal hormones and on puberty in female goats

The aim of the present study was to investigate if environmental doses of PCB 153 and PCB 126 could produce effects in a controlled animal model. Possible adverse effects on the hypothalamic-pitutitary-gonadal axis were examined by measuring gonadotrophins and gonadal steroid hormone concentrations in goat kids exposed during gestation and lactation. The concentrations of PCB 153 and PCB 126 in adipose tissue in the goat kids 9 months post-partum were 5800 ng/g (fat-weight, range; 2900-12700 ng/g) and 0.49 ng/g (fat-weight, range; 0.28-0.80 ng/g), respectively. The pre- and post-pubertal plasma concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH), prolactin (Prl) and progesterone (P4) were analysed. LH, FSH, Prl, and P4 were also measured during an induced oestrus cycle. The prepubertal LH concentration was significantly lower, the puberty was delayed and the P4 level during the luteal phase of an estrous cycle was higher in the group exposed to PCB 153. No significant effect of PCB 153 exposure was found on Prl and FSH. PCB 126 did not produce any effects at the exposure level tested in this study. In conclusion, perinatal exposure to PCB 153 affected the reproductive function and the puberty maturation in goats.

Exposure to PCBs and p,p'-DDE and human sperm chromatin integrity

Persistent organochlorine pollutants (POPs) such as polychlorinated biphenyls (PCBs) and dichlorodiphenyldichloroethylene (p,p'-DDE), the major metabolite of dichlorodiphenyltrichloroethane (DDT), are stable lipophilic compounds widely found in the environment and in the general population. They can enter the food chain, and their negative impact on male reproduction is currently under active scrutiny. To explore the hypothesis that environmental exposure to these compounds is associated with altered sperm chromatin structure integrity in human sperm, we conducted a study of 176 Swedish fishermen (with low and high consumption of fatty fish, a very important exposure source of POPs). We determined serum levels of 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153) and p,p'-DDE, and we used the sperm chromatin structure assay (SCSA) to assess sperm DNA/chromatin integrity. When CB-153 serum levels (individual dose range, 39-1,460 ng/g lipid) were categorized into equally sized quintiles, we found an association with the DNA fragmentation index (%DFI). A significantly lower %DFI was found in the lowest CB-153 quintile (< 113 ng/g lipid) compared with the other quintiles; there was a similar tendency, although not statistically significant, between %DFI and p,p'-DDE. These results suggest that POP exposure may have a slight negative impact on human sperm chromatin integrity.

Toxic and hormonal effects of polychlorinated biphenyls on cultured testicular germ cells of embryonic chickens

The toxic and hormonal effects of polychlorinated biphenyls (PCBs) on testicular germ cell development were revealed with a germ-Sertoli cell co-culture model from embryonic chickens. Testicular cells were dispersed from 18-day-old embryo and exposed to Aroclor 1254 (A1254) alone and combined with alpha-tocopherol, flutamide and tamoxifen for discretion of the toxic and hormonal actions of A1254. Cell damage was evaluated by determinations of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) reduction and lactate dehydrogenase (LDH) leakage. Results showed that 10 microg/ml A1254 induced condensed nuclear and vacuolated cytoplasm; cell exfoliated and broke into pieces as a sign of cell degeneration after treatment for 6 h. The morphological cytotoxicity was confirmed by MTT reduction and LDH leakage assays. alpha-Tocopherol attenuated the toxic effect of A1254. After culture for 48 h, A1254 (0.1-1 microg/ml) manifested obvious hormonal effect to induce germ cell proliferation, while 10 microg/ml A1254 displayed obvious toxic and hormonal effects on germ and somatic cells. Blocking of either androgen receptor by flutamide or estrogen receptor by tamoxifen inhibited hormonal effect of A1254 on germ cell proliferation and increased the cytotoxicity. The above results indicated that A1254 exposure imposed both toxic and hormonal effects on embryonic testicular germ cell proliferation, which may cause reproductive disorder and even infertility at adulthood.

Increased serum and testicular androgen levels in F1 rats with lifetime exposure to soy isoflavones

The consequences of dietary soy isoflavones on serum and testicular androgen levels were examined in F1 male rats from a multigeneration study investigating the effects of diets varying in isoflavone content. Rats were fed either a soy-free casein based diet (AIN93G) or a diet in which alcohol-washed soy protein replaced casein as the protein source and to which increasing amounts of Novasoy, a commercially available isoflavone supplement were added. Analysis of these diets showed that the isoflavone content in each diet was 0 (diet 1; casein based control), 31.7 (diet 2; alcohol-washed soy-based diet control), 36.1 (diet 3), 74.5 (diet 4), 235.6 (diet 5) and 1046.6 (diet 6) mg total isoflavones/kg pelleted diet. The levels of isoflavones in diet 1 would represent a daily intake level of 0 mg isoflavones, diets 2 and 3 estimate a low soy-containing human diet (e.g. North American), diet 4 would correspond to Asian diets (e.g. Japanese) or adult humans taking isoflavone supplements, diet 5 approximates the isoflavone intake by babies fed soy based infant formula and diet 6 approximates fivefold the intake levels by babies or 10-fold the intake levels of adults consuming high isoflavone containing diets. Serum testosterone (T) from F1 male rats sacrificed on postnatal days (PND) 28, 70, 120, 240 and 360 were low at PND 28 (0.4 ng/ml), increased approximately five to sixfold at PND 70 (2.5-3.0 ng/ml) and thereafter declined to a steady state level of approximately 1 ng/ml by PND 120. However, rats on diets 5 and 6 demonstrated altered serum testosterone profiles such that at days 120, testosterone levels remained significantly elevated at approximately 3 ng/ml (P < 0.05). Serum dihydrotestosterone levels exhibited similar profiles and the levels in PND 120 rats on diet 5 or 6 were also significantly elevated (two to threefold, P < 0.05). The intra-testicular testosterone concentration in rats on diet 5 was also elevated at PND 120 compared with diet 1 (P < 0.05). These findings show that F1 male rats continuously exposed to a mixture of dietary soy isoflavones from conception onwards exhibit altered serum and testicular androgen profiles.

Establishment of a germ-somatic cell coculture model for toxicity assessment of environmental endocrine disrupters

The objective of this study was to evaluate the effect of environmental endocrine disrupting chemicals by a germ--somatic cell coculture model in vitro. Testicular cells of 18-day-old chicken embryos were dispersed and cultured in different media. Results showed that somatic cells formed a monolayer to which germ cells adhered in the medium supplemented with insulin (Ins), transferrin (Tf), and selenite (Se) (ITS medium). However, the medium without ITS or single subtraction of Ins, Tf, or Se could not maintain cell survival in culture because many germ cells manifested apoptosis. Three known endocrine disrupters were selected to test the feasibility of this model. Aroclor 1254 (A1254, 10 microg/mL) induced condensed nuclei and vacuolated cytoplasm in germ cells, which was further confirmed by a cell proliferation assay. However, after culture for 48 h, the number of germ cells displayed a significant augment stimulated by A1254 (0.1-10 microg/mL) (P < 0.05). Similarly, 2,4-dichlorophenoxyacetic acid and busulfan displayed notable toxic effects on germ cells, and germ cell number and cell viability were significantly decreased in a dose-dependent manner (P < 0.05). The above results indicate that the chicken testicular germ-somatic cell coculture model is a simple, rapid, and veracious in vitro tool for evaluating the effect of environmental endocrine disrupters on functional basis of the cultured cells.

Suppression of aromatase activity in vitro by PCBs 28 and 105 and Aroclor 1221

The effects of polychlorinated biphenyls (PCBs) on human cytochrome P450 aromatase activity in vitro were investigated using a commercially available microsomal fraction obtained from baculovirus infected insects that had been transfected with the human CYP19 gene and cytochrome P450 reductase. The assay measured the conversion of tritiated testosterone to estradiol in Tris buffer at pH 7.4. When aroclors, commercial preparations of PCBs, were added to aromatase assays at a 10 microM concentration, Aroclor 1221 caused a reduction in the aromatase activity, whereas other aroclors (1016, 1232, 1242, 1248, 1254, 1260, 5432, 5442 and 5460) were without effect. Further investigation of the effect of Aroclor 1221 on aromatase activity showed that the inhibition was dose dependent. When a reconstituted mixture (RM) of PCBs that represented the congeneric content of human milk was investigated, no inhibition of aromatase activity at the maximum treatment of 15.0 microM was observed. None of the congeners present in the reconstituted mixture, except PCB 28 and 105, affected P450 arom activity. PCB 28 showed a statistically significant inhibition of aromatase activity (P<0.05) at 1.5 and 15 microM and a significant inhibition of aromatase activity by PCB 105 was also observed, but only at 15 microM. In three separate kinetic analyses the Km(app) for aromatase was 64, 89 and 69 nM (mean 74 nM). In addition, PCB 28 resulted in an increase in the Km(app) without a significant effect on Vmax(app), suggesting competitive inhibition by this congener. This conclusion was supported by slope (Km(app)/Vmax(app) versus [inhibitor]) and intercept (1/Vmax(app) versus [inhibitor]) replots. The slope replots gave Ki(app) values for PCB 28 of 0.9, 1.3 and 2.0 microM (mean 1.4 microM), whereas intercept replots were almost horizontal. Thus, PCB 28 is a competitive inhibitor of aromatase with a Ki(app) value approximately 20-fold the Km(app) value. Based on these studies, we conclude that most PCBs are not inhibitors of aromatase activity in vitro. However, as being inhibitors of aromatase activity, Aroclor 1221, PCB 28 and PCB 105 would remain a priority for further study as possible endocrine disrupters.

Effects of acute postnatal exposure to 3,3',4,4'-tetrachlorobiphenyl on sperm function and hormone levels in adult rats

Polychlorinated biphenyls (PCBs) are considered potential endocrine disruptors due to their ability to act as estrogens, antiestrogens and goitrogens. The aim of this study is to ascertain whether acute postnatal treatment with 3,3',4,4'-tetrachlorobiphenyl (CB 77) affects sperm function and hormone levels in adult rats. Male Sprague-Dawley rats received CB 77 by ip injection of 2 or 20 mg/kg at day 21 and sacrificed at day 112. At day 112, right and left testis weights were significantly increased, whereas sperm count, motility, total motile sperm count, curvilinear velocity, average path velocity, straight-line velocity, and beat-cross frequency for motile sperm were significantly decreased in rats treated with 20 mg/kg CB 77. Sperm-oocyte penetration rate was significantly reduced in rats treated with either 2 or 20 mg/kg CB 77. There was high sperm acrosome reaction rate (ARR) in the 20 mg/kg CB 77-treated rats. There was a significant increase in thyroid-stimulating hormone level in the 20 mg/kg CB 77 group. However, no changes were seen in serum testosterone, thyroid hormones, or prolactin concentrations at day 112. In summary, this study showed that postnatal exposure to CB 77 might affect spermatogenesis, motility, ARR, and ability of fertilizing oocytes in mature rats. These results suggest that the sperm functions may be more susceptible or adapt less readily than the thyroid functions to endocrine disruption caused by dioxin-like PCB congeners.

Thyroid hormone, glucocorticoids, and prolactin at the nexus of physiology, reproduction, and toxicology

A symposium at the 2003 Annual Meeting of the Society of Toxicology brought together an expert group of endocrinologists to review how non-reproductive hormones can affect the endocrine system. This publication captures the essence of those presentations. Paul Cooke and Denise Holsberger recapitulate the evidence of how thyroid hormones affect male and female reproduction, and reproductive development. Ray Witorsch summarizes the many effects of glucocorticoids on the reproductive system. Finally, Paul Sylvester reviews the mechanism of action of prolactin, and reminds us that this ancient hormone has many functions beyond lactation.

Developmental Hormonal Profiles in rdw Rats with Congenital Hypothyroidism Accompanying Increased Testicular Size and Infertility in Adulthood

Congenital hypothyroid mutant male rdw rats have enlarged testes in adulthood with dwarfism accompanied by infertility. To explain how rdw rats acquire enlarged testes in adulthood, we compared age-matched normal (N) rats at various developmental stages for blood levels of hormones, thyroxine (T4), follicle stimulating hormone (FSH), luteinizing hormone (LH) and testosterone (T), and investigated whether T4 therapy (rdw+T4) from 3 weeks of age (w) until adulthood could induce recovery of fertility in rdw rats, as well as how rdw+T4 affected hormonal patterns. Testes weights of rdw rats were higher than those of N rats at 19 w in adulthood though it was low during development. Serum T4 values in rdw rats were markedly lower than those in N rats but steadily increased up to 19 w. The serum FSH values in rdw rats were lower than those in N rats at all ages, and neither serum LH nor T value was significantly different at any age. The testes weight of rdw+T4 rats was significantly higher than that of N rats at 13 w with recovered growth, and was higher than that of rdw rats at 19 w. When they were mated with proestrous females after 16 w, all females became pregnant and gave birth to a normal number of pups. The T4 and FSH values of rdw+T4 rats were significantly higher than those in rdw rats, but similar to those in N rats in adulthood. The results suggest that even low levels of circulating thyroid hormone (TH) in rdw rats stimulate the development of their testes, probably through Sertoli cells, resulting in the enlarged adult testes without fertility, and that a sufficient circulating TH level from the immature stage plays a pivotal role in restoring mating activity, probably through FSH-mediated action towards adulthood.

Testicular histopathology in deer mice (Peromyscus maniculatus) following exposure to polychlorinated biphenyl

Adult deer mice testes were subjected to routine histopathology following exposure to Aroclor 1254 supplemented diet (5 ppm), for 30 days. Body and testicular weight revealed no statistical significance between the control and treated animals. From a histological standpoint the testes of the controls were similar to normal murids and other animals. In contrast, the testes from treated animals displayed seminiferous tubules with significant degenerative alterations. These alterations included fewer layers of seminiferous epithelium exaggerated intercellular spaces and appearance of pyknotic nuclei. Most tubules displayed subluminal nuclei that morphologically could be identified as part of spermatozoa heads and these usually lacked tails, indicating that the treatment interfered with spermiogenesis. Therefore, we concluded that Aroclor 1254 as an environmental contaminant is highly destructive to seminiferous tubules, and that these histological alterations undoubtedly are responsible for the depressed fertility in Peromyscus following chronic exposure to PCBs, that has been reported in the literature.

Effects of subchronic exposure to a complex mixture of persistent contaminants in male rats: systemic, immune, and reproductive effects

Human populations throughout the world are exposed daily to low levels of environmental contaminants. The consequences of potential interactions of these compounds to human endocrine, reproductive, and immune function remain unknown. The current study examines the effects of subchronic oral exposure to a complex mixture of ubiquitous persistent environmental contaminants that have been quantified in human reproductive tissues. The dosing solution used in this study contained organochlorines (2,3,7,8-tetrachlorodibenzo-p-dioxin [TCDD], polychlorinated biphenyls [PCBs],p,p'-dichlorodiphenoxydichloroethylene [p,p'-DDE],p,p-dichlorodiphenoxytrichloroethane [p,p'-DDT], dieldrin, endosulfan, methoxychlor, hexachlorobenzene, and other chlorinated benzenes, hexachlorocyclohexane, mirex and heptachlor) as well as metals (lead and cadmium). Each chemical was included in the mixture at the minimum risk level (MRL) or tolerable daily intake (TDI) as determined by the U.S. EPA or ATSDR or, for TCDD, at the no observable effect level (NOEL) used to calculate the TDI. Sexually mature male rats were exposed to this complex mixture at 1, 10, 100, and 1000 times the estimated safe levels daily for 70 days. On day 71, all animals were sacrificed and a variety of physiological systems assessed for toxic effects. Evidence of hepatotoxicity was seen in the significant enlargement of the liver in the 1000x group, reduced serum LDH activity (100x), and increased serum cholesterol and protein levels (both 1000x). Hepatic EROD activities were elevated in animals exposed to10x and above. The mixture caused decreased proliferation of splenic T cells at the highest dose and had a biphasic effect on natural killer cell lytic activity with an initial increase in activity at 1x followed by a decrease to below control levels in response to 1000x. No treatment-related effects were seen on bone marrow micronuclei, daily sperm production, serum LH, FSH, or prolactin levels or weights of most organs of the reproductive tract. The weights of the whole epididymis and of the caput epididymis were significantly decreased at 10x and higher doses, although no effect was seen on cauda epididymal weight. The sperm content of the cauda epididymis was increased at the 1x level but not significantly different from control at higher dose levels. A slight, but significant, increase in the relative numbers of spermatids was seen in the animals from the 1000x group with a trend towards reduced proportion of diploid cells at the same dose. Only minor, nondose related changes were seen in parameters related to condensation of chromatin, as determined by flow cytometry, in epididymal sperm. We conclude that the mixture induced effects on the liver and kidney and on general metabolism at high doses but caused only minor effects on immune function, reproductive hormone levels, or general indices of reproductive function measures. These data suggest that additive or synergistic effects of exposure to contaminants resulting in residue levels representative of contemporary human tissue levels are unlikely to result in adverse effects on immune function or reproductive physiology in male rats.

Effects of gestational and lactational exposure to Aroclor 1242 on sperm quality and in vitro fertility in early adult and middle-aged mice

The objective of this study was to examine the effects of gestational and lactational exposure to Aroclor 1242 (0, 10, 25, 50, and 100 mg/kg-bw) on male fertility. Doses were administered to C57BL6 female mice orally every two days from two weeks before mating, during mating, and through gestation until postnatal day 21. Male B6D2F1 offspring were examined for anogenital distance, organ development, epididymal sperm count, sperm motility, and in vitro fertility at 16 and 45 weeks of age. Stomach samples of pups nursing from PCB-treated mothers in the 50 mg/kg dose group were analyzed for PCBs and chlorobiphenylols by high resolution gas chromatography coupled with low resolution mass spectrometry. It was estimated that the nursing pups were exposed to 0.2, 0.6, 1.2, and 2.4 mg/kg/day total PCBs in the 10, 25, 50, and 100 mg/kg dose groups, respectively. This exposure level approaches the maximum FDA recommended levels for PCBs in food and breast milk. The composition of the PCBs in the stomach samples was different from the parent mixture, as there was a higher proportion of heavily chlorinated congeners, as well as chlorobiphenylols. Anogenital distance at weaning, and liver, thymus, and testes weight at 16 and 45 weeks of age were not affected by PCB exposure. Epididymal sperm velocity and linearity were significantly increased in the 25 mg/kg dose group at 16 weeks of age. Sperm count was increased by 36% in this dose group (P = 0.06). By 45 weeks of age, average sperm count in this dose group was similar to that of controls. With the exception of the 50 mg/kg dose group at 16 weeks of age, sperm fertilizing ability in vitro was significantly decreased in all PCB-exposed groups at 16 and 45 weeks of age. These results suggest that fertility in the adult mouse is susceptible to developmental exposure to Aroclor 1242 and is independent of testis weight or epididymal sperm count.

Effects of continuous and intermittent exposure of lactating mothers to aroclor 1242 on testicular steroidogenic function in the adult male offspring

Polychlorinated biphenyls (PCBs) are worldwide pollutants and have caused hazardous effects on many animal species including humans. They have been detected in human milk and therefore exposure of newborns to PCBs is unavoidable if they are breast-fed. We present our findings on two experiments performed to test the effects of intermittent and continuous exposure of lactating rats to two different doses (80 microg and 8 microg) of Aroclor 1242 (a PCB congener) on testicular steroidogenic function of their adult male offspring. In experiment I, three groups of lactating dams received daily subcutaneous (SC) injections of either corn oil, 80 microg of Aroclor 1242 and 8 microg of Aroclor 1242 in corn oil, respectively. In experiment II, three groups of lactating dams received two SC injections per week of either corn oil or Aroclor 1242 (80 microg and 8 microg) in corn oil, respectively. Pups in all groups (n=8 per group) were weaned at day 21 and were raised on a normal diet until sacrificed at 90 days. Experiment I: Leydig cell number per testis was significantly (P<0.05) increased and the average volume of a Leydig cell was significantly (P<0.05) reduced in both groups of Aroclor-exposed rats compared to corn oil controls. Both doses of Aroclor resulted in reduced (P<0.05) serum testosterone levels compared to corn oil-treated controls. LH-stimulated testosterone production per testis and per Leydig cell was lower in Aroclor-exposed rats compared to controls. Experiment II: No changes were observed in Leydig cell size and number per testis among the three groups. Serum LH, testosterone and LH-stimulated testicular testosterone production in offspring rats of Aroclor-treated dams were not significantly different (P>.05) from the offspring of corn oil-treated dams. However, these parameters were lower in value in the offspring of dams treated with Aroclor 80 microg compared to the other two groups. LH-stimulated testosterone secretory capacity per Leydig cell was significantly lower in offspring of dams treated with Aroclor compared to controls. Serum T4 and T3 levels were not significantly different among the Aroclor-exposed and control rats in both experiments. These results demonstrate that continuous exposure of lactating mothers to 8 and 80 microg of Aroclor 1242 causes hypotrophy and malfunctioning of Leydig cells in the adult male offspring resulting in a hypoandrogenic status. Intermittent treatment of lactating mothers with 80 microg of Aroclor (but not with 8 microg of Aroclor) also produced malfunctioning of Leydig cells and a hypoandrogenic status in the absence of Leydig cell hypotrophy. However, the Aroclor 8 microg dose was ineffective to produce the above effects.

Effects of polychlorinated biphenyls on development and reproduction

As part of its mandate, the Agency for Toxic Substances and Disease Registry (ATSDR) prepares toxicological profiles on hazardous chemicals found at Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priorities List (NPL) sites that have the greatest public health impact. These profiles comprehensively summarize toxicological and environmental information. This article, which constitutes the release of an important section of the Toxicological Profile for Polychlorinated Biphenyls (ATSDR 2000) into the scientific literature, focuses on the developmental and reproductive effects of this group of synthetic organic chemicals (PCBs) in humans and animals. Information on other health effects, toxicokinetics, mechanisms of toxicity, biomarkers, interactions, chemical and physical properties, potential for human exposure, and regulations and advisories is detailed in the profile. Interested readers are encouraged to consult the original toxicological profile for more information. Profiles can be requested from ATSDR's Information Center by telephone (1-888-42-ATSDR [1-888-422-8737] or E-mail: (atsdric@cdc.gov).

Effects of exposure of lactating female rats to polychlorinated biphenyls (Pcbs) on testis weight, sperm production and sertoli cell numbers in the adult male offspring

To investigate the effects of intermittent and continuous exposure of lactating rats to Aroclor 1242 (a PCB congener), testis weight, daily sperm production (DSP) and Sertoli cell number per testis were examined in the adult male offspring. Thyroxine (T4) was also measured because of the well-documented effects of polychlorinated biphenyls (PCBs) on this hormone. In experiment 1.3 groups of lactating female rats received daily subcutaneous injections of low (0.8 mg) or high (1.6 mg) doses of Aroclor 1242 in 0.1 ml corn oil from parturition to weaning of pups at 21 days. In experiment II, 3 groups of lactating rats received 2 subcutaneous injections per week of 0.8 or 1.6 mg Aroclor 1242, as in experiment 1. In both experiments, control rats received vehicle alone. Serum T4 was measured at 21 and 90 days of age, and testis weight, DSP and Sertoli cell numbers were examined at 90 days. In experiment I (continuous exposure), both the low (0.8 mg) and high (1.6 mg) doses suppressed T4 concentrations at 21 days of age. Testis weight was increased by 14.8% (LD) and 16.5% (HD) compared with controls. DSP was increased by 20.4% in the low dose and 25% in the high dose animals compared with controls. The number of Sertoli cells per testis was increased by 32.6 and 39.4% in low and high dose animals, respectively. A similar study in which the lactating females were only dosed twice per week (experiment 11) did not show any differences in these parameters. These results indicate that continuous exposure of lactating female rats to PCBs increases testis weight, sperm production and Sertoli cell numbers in the adult male offspring.