A 28-day oral dose toxicity study in Wistar rats enhanced to detect endocrine effects of decabromodiphenyl ether (decaBDE)

Decabromodiphenyl ether (decaBDE) is a widely used brominated flame retardant, considered to be of low toxicity. However, previous toxicity studies applied exposure methods with low bioavailability of this compound, and the actual hazard of decaBDE for humans, which are environmentally exposed to decaBDE, may thus be underestimated in current risk assessments. The present 28 days oral toxicity study in Wistar rats was designed to facilitate detection of endocrine and immune modulating effects of decaBDE using an exposure protocol with improved bioavailability. A technical preparation of high purity decaBDE was thus tested by daily exposure through gavage with an emulsion of soy phospholipon/lutrol as a carrier. Most sensitive effect in males were increased weight of seminal vesicle/coagulation gland with BMDL of 0.2mg/kg bw/day and increased expression of hepatic CYP1A and CYP2B (BMDLs 0.5-0.7 mg/kg bw/day). In females the most sensitive effect was decreased activity of P450c17 (CYP17), which is a key enzyme in the androgen synthesis pathway, in adrenals (BMDL 0.18 mg/kg bw/day). These results suggest that decaBDE may represent an as yet unreported hazard for reproductive health.     

A 28-day oral dose toxicity study enhanced to detect endocrine effects of a purified technical pentabromodiphenyl ether (pentaBDE) mixture in Wistar rats

A 28-day subacute oral toxicity study was performed in Wistar rats with a purified preparation of the commercial pentabromodiphenyl ether (pentaBDE), DE-71. The applied OECD407 protocol was enhanced for endocrine and immune parameters, and to enable benchmark dose analysis. A vehicle control group and 7 dose groups were included, which received 0.27, 0.82, 2.47, 7.4, 22.2, 66.7 or 200 mg pentaBDE/kg bw/d (mkd). The liver appeared to be a key target organ, showing a marked increase of weight and centrilobular hepatocellular hypertrophy, probably due to the observed induction of P450 enzymes, notably CYP1A and CYP2B. A marked decrease of circulating total thyroxine (TT4) and an increase of plasma cholesterol were probably secondary to the liver effects. Furthermore, dose-dependently decreased weight of epididymis, seminal vesicles, and prostate, as well as sperm head deformities in males, and induction of CYP17 activity in adrenals in females were observed, all possibly related to anti-androgenic activity. Finally, we observed a substantial increase of large unstained cells in the blood and a decrease of apolar retinoids in the liver. All these effects had benchmark doses at the lower confidence bound (BMDL) in the low- or mid-dose range, but particular sensitive, potentially adverse effects were TT4 decrease (BMDLs 1.1 in males and 1.8 mkd in females), and decrease of hepatic apolar retinoids (BMDLs 0.5 mkd in males and 2.3 mkd in females). These results contribute to refinement of the hazard identification of pentaBDE and improved risk assessment of human exposure to this industrial chemical and environmental pollutant.     

Endocrine effects of hexabromocyclododecane (HBCD) in a one-generation reproduction study in Wistar rats

The brominated flame retardant (BFR) hexabromocyclododecane was tested in a one-generation reproduction assay in Wistar rats, enhanced for endocrine parameters. A solution of the compound in corn oil was mixed in the feed, targeting at dietary exposure of 0–0.1–0.3–1–3–10–30–100 mg/kg body weight/day (mkd) in parental rats during 10 (males) or 2 (females) weeks premating, during gestation and lactation, and in their F1 offspring from weaning until final necropsy. Effects were assessed in F1 animals. Livers of these animals showed increased HBCD concentrations, in a dose-dependent way. The trabecular bone mineral density of the tibia was dose-dependently decreased in females (BenchMark Dose Lower confidence bound, BMDL = 0.056 mkd). The IgG response after immunization with sheep red blood cells (SRBC) was increased in males (BMDL = 0.46 mkd). Further sensitive effects were decreased weight of the testis (BMDL = 1.5 mkd), increased fraction of neutrophilic granulocytes (BMDL = 7.7 mkd), decreased concentration of apolar retinoids in female livers (BMDL = 1.3 mkd), and decreased plasma alkaline phosphatase in females (BMDL = 8.6 mkd). CYP19/aromatase activity in the ovary was correlated to the concentration of γ-HBCD in the liver. A developmental origin of these effects is considered, and this is also true for sensitive effects observed in neurobehavioural testing in littermates from the same experiment, i.e. in the brainstem auditory evoked potentials and in a catalepsy test [Lilienthal, H., Van der Ven, L.T.M., Piersma, A.H., Vos, J.G. Neurobehavioral effects of the brominated flame retardant hexabromocyclododecane (HBCD) in rats after pre- and postnatal exposure, in press]. The low BMDLs of these effects may raise concern for human health, particularly when based on body burdens of HBCD, which leads to critical margins of exposure particularly for the occupational setting.     

Tamoxifen: 28-day oral toxicity study in the rat based on the Enhanced OECD Test Guideline 407 to detect endocrine effects

The main objective of this 28-day oral gavage toxicity study in the rat was to investigate which of the current and/or additional parameters of the OECD Test Guideline 407 would reliably and sensitively detect the endocrine-mediated effects of the nonsteroidal antiestrogen tamoxifen. In addition, as this study was performed using two subgroups of five animals of each sex run concurrently, it enabled an assessment of the intralaboratory reproducibility while also assessing the potential value of using ten animals of each sex per group instead of using the standard five animals of each sex per group stipulated by the current guideline. Tamoxifen was administered daily by gavage to groups of 7-week-old Wistar rats for at least 28 days at dose levels of 5, 30, or 200 µg/kg body weight. Additional parameters specified in the enhanced OECD Test Guideline 407 were spermatozoa enumeration and morphology of the cauda epididymis, hormonal analysis of the thyroid-stimulating hormone (TSH), triiodothyronine (T₃) and thyroxine (T₄) levels, monitoring of the estrous cycle during week 4 of treatment to ensure females were in diestrus on the day of terminal sacrifice, organ weight of ovary, uterus, thyroid gland, prostate gland (ventral and dorsolateral parts), seminal vesicles with coagulation glands and pituitary gland, and microscopic investigation of the pituitary gland, vagina, mammary gland, seminal vesicles with coagulating glands, epididymis, and prostate gland (ventral and dorsolateral parts). Overall, 200 µg/kg per day was considered to be the Maximum Tolerated Dose (MTD) in both sexes, resulting in a marked reduction of body weight gain, together with slight effects on clinical signs, hematology, plasma chemistry, and microscopic changes in some endocrine tissues. Five micrograms per kilogram per day represented the No Observed Adverse Effect Level (NOAEL) in males and the No Observed Effect Level (NOEL) in females. At the intermediate dose level (30 µg/kg per day), the current OECD Test Guideline 407 was appropriate to detect the specific endocrine-related changes induced by tamoxifen in females, based on the histopathology findings observed in the ovary and the uterus. The additional parameters which were found to be changed in females (thyroid hormone levels, ovary and uterus weights, and histopathology of vagina) provided supplementary information further confirming tamoxifen-mediated endocrine effects. In males, when data from the current Test Guideline 407 were considered at the intermediate dose level, specific endocrine effects were only indicated on the basis of the histopathology findings observed in the prostate gland. The additional parameters examined which were found to be changed (prostate gland and seminal vesicle weights, and histopathology of seminal vesicle and mammary gland) were necessary to confirm the specific tamoxifen-mediated endocrine effects. Hence, amongst the additional parameters contained in the enhanced OECD Test Guideline 407, organ weights and histopathological examination of endocrine-related organs were the most helpful in confirming the detection of tamoxifen-mediated endocrine effects. The reproducibility evaluation showed that a group size of five animals of each sex consistently allowed the detection of endocrine effects with the current Test Guideline in both sexes at the high dose level and in females at the intermediate dose level. Doubling the animal number from five to ten of each sex per dose level did not notably increase the sensitivity of detection of endocrine-mediated effects.     

A 28-day oral toxicity study of echimidine and lasiocarpine in Wistar rats

Pyrrolizidine alkaloids (PAs) are a class of naturally-occurring plant toxins. Echimidine is one of the predominant PAs found in honeys produced in Australia and New Zealand. There is a lack of information on the oral toxicity of echimidine on which to base regulatory decisions concerning the risk to humans of these honeys. This GLP study was conducted to assess the subchronic dietary toxicity of echimidine to rats compared to that of lasiocarpine as a positive control. Wistar rats, 10/sex, were fed diets containing 0, 0.6, 1.2 or 2.5 mg/kg bw echimidine. Positive control groups, 10/sex, were fed diets containing 0.6, 1.2 or 2.5 mg/kg bw lasiocarpine.Neither PA had any effect on survival, food consumption, clinical signs, gross lesions, or histopathology. Consumption of lasiocarpine, but not echimidine, decreased bodyweight gain in males at ≥ 1.2 mg/kg bw, and in females at 2.5 mg/kg bw. Slight alterations in white cell counts and serum ALT concentrations at 2.5 mg/kg bw of both PAs were not clinically significant, had no histological correlates, and were considered to be of equivocal relevance.In conclusion, the subchronic No Observed Adverse Effect Level (NOAEL) for echimidine is 2.5 mg/kg bw/day, whereas, on the basis of a treatment-related decrease in bodyweight gain in males at 1.2 mg/kg bodyweight, the NOAEL for lasiocarpine is 0.6 mg/kg bw/day.     

A repeated dose 28-day oral toxicity study of extract from cultured Lentinula edodes mycelia in Wistar rats

To evaluate the toxicological safety of extract from cultured Lentinula edodes mycelia (L.E.M.), repeated doses (2,000 mg/kg/day) were administered to male and female Wistar rats for 28 days. No mortality or abnormality in the general status or appearance was observed in rats administered L.E.M extract. Body weight and food consumption decreased slightly, particularly in the case of male rats, although the degree of decrease was not as prominent toward the end of administration. Examination of hematology, serum biochemistry, absolute and relative organ weights, autopsy and histopathology revealed only a few statistically significant differences between the treatment and control groups; these differences suggested no clinically significant changes related to toxicity. Consequently, the no observed adverse effect level (NOAEL) of L.E.M. extract was considered to be more than 2,000 mg/kg/day under the conditions of the present study.     

A 15-day oral dose toxicity study of aspirin eugenol ester in Wistar rats

The subchronic toxicity of aspirin eugenol ester (AEE) was evaluated after 15-day intragastrically administration in rats at daily doses of 50, 1000, and 2000 mg/kg. AEE at low-dose showed no toxicity to the tested rats. Following repeated exposure to medium- or high-dose of AEE, apparent changes were observed in the levels of blood glucose, AST, ALP, ALT and TB in both male and female rats, and appeared to be dose-independent. There were no significant gender differences in most indexes of subchronic toxicity throughout the experimental period with the exception of food consumption and body weight. The no-observed-adverse-effect level (NOAEL) of AEE was considered to be 50 mg/kg/day under the present study conditions.     

Toxicokinetics of tetrabromobisphenol a in humans and rats after oral administration.

Tetrabromobisphenol A (TBBPA) is widely used as a flame retardant and is suspected to be stable in the environment with possible widespread human exposures. This study reports the characterization of the toxicokinetics of TBBPA in human subjects and in rats. A single oral dose of 0.1 mg/kg TBBPA was administered to five human subjects. Rats were administered a single oral dose of 300 mg TBBPA/kg body weight. Urine and blood concentrations of TBBPA and its metabolites were determined by LC/MS-MS. TBBPA-glucuronide and TBBPA-sulfate were identified as metabolites of TBBPA in blood and urine of the human subjects and rats. In blood, TBBPA-glucuronide was detected in all human subjects, whereas TBBPA-sulfate was only present in blood from two individuals. Maximum plasma concentrations of TBBPA-glucuronide (16 nmol/l) were obtained within 4 h after administration. In two individuals where TBBPA-sulfate was present in blood, maximum concentrations were obtained at the 4-h sampling point; the concentrations rapidly declined to reach the limit of detection (LOD) after 8 h. Parent TBBPA was not present in detectable concentrations in any of the human plasma samples. TBBPA-glucuronide was slowly eliminated in urine to reach the LOD 124 h after administration. In rats, TBBPA-glucuronide and TBBPA-sulfate were also the major metabolites of TBBPA present in blood; in addition, a diglucuronide of TBBPA, a mixed glucuronide-sulfate conjugate of TBBPA, tribromobisphenol A, and the glucuronide of tribromobisphenol A were also present in low concentrations. TBBPA plasma concentrations peaked at 103 micromol/l 3 h after administration and thereafter declined with a half-life of 13 h; maximal concentrations of TBBPA-glucuronide (25 micromol/l) were also observed 3 h after administration. Peak plasma concentrations of TBBPA-sulfate (694 micromol/l) were reached within 6 h after administration. The obtained results suggest absorption of TBBPA from the gastrointestinal tract and rapid metabolism of the absorbed TBBPA by conjugation resulting in a low systemic bioavailability of TBBPA.     

28-day repeated dose oral toxicity of recombinant human holo-lactoferrin in rats

Recombinant human holo-lactoferrin (holo-rhLF) was orally administered, via gavage, to Wistar rats at 1000, 500 and 100mg/kgbw/day for 28 days. The test article, holo-rhLF, was expressed in rice grain, extracted, purified and saturated with iron. During the 28-day period, animals were examined for evidence of toxicity. On day 29, the animals were exsanguinated, examined for gross pathology, and tissues preserved for histopathology. There were no deaths caused by holo-rhLF and in-life physical signs were generally normal. Although statistical differences were noted in some hematology, clinical chemistry and heart/body weight ratios, they were of questionable biological significance. A significantly greater total iron binding capacity (TIBC) was detected in the blood of male animals dosed with holo-rhLF. Serum was analyzed for the presence of IgG and IgE antibodies; demonstrating low levels of IgG antibodies to the human protein, but no increase in IgE antibodies. There was no increase in serum lactoferrin levels. The results of the 28-day oral administration demonstrate a lack of toxicity of holo-rhLF in rats. There were no treatment related, toxicologically relevant changes in clinical signs, growth, food consumption, hematology, clinical chemistry, organ weights or pathology. The no observed adverse effect level (NOAEL) is greater than 1000 mg/kg/day.     

A 90-day drinking water toxicity study in rats of the environmental contaminant ammonium perchlorate.

Perchlorate (ClO(4)(-)), the dissociated anion of perchlorate salts such as ammonium, potassium, and sodium perchlorate, has been recently recognized as a persistent and pervasive contaminant of drinking water supplies in a number of metropolitan areas. Perchlorate is of concern because of uncertainties in the toxicological database available to address the potential human health effects of low-level exposure. The purpose of this study was to evaluate the subchronic toxicity of perchlorate when administered to Sprague-Dawley rats as ammonium perchlorate (AP) for 14 or 90 days. The study consisted of an untreated control group and five treatment groups that received continuous exposure to AP via the drinking water at dosage levels of 0.01, 0.05, 0.2, 1.0, and 10.0 mg/kg/day. The study design included a nontreatment recovery period of 30 days to evaluate the reversibility of any AP-induced effects at the 0.05, 1.0, and 10.0 mg/kg/day levels. The study also investigated the potential effects of AP on male sperm parameters, female estrous cyclicity, bone marrow micronucleus formation, and serum hormone levels, i.e., triiodothyronine (T(3)), thyroxine (T(4)), and thyroid stimulating hormone (TSH). No toxicologically meaningful differences were observed between the control and AP-treated groups with respect to survival, clinical observations, body weights, food consumption, water consumption, ophthalmology, hematology, clinical chemistry, estrous cycling, sperm parameters, or bone marrow micronucleus formation. A target organ effect was produced by AP in the thyroids of male and female rats at the 10 mg/kg/day level after 14 and 90 days of exposure. The effect was characterized by significantly increased thyroid weights and thyroid histopathology consisting primarily of follicular cell hypertrophy with microfollicle formation and colloid depletion. These changes were reversible after a nontreatment recovery period of 30 days. Statistically significant changes in TSH and thyroid hormones were observed at all AP dosage levels tested; however, no thyroid organ weight or histopathological effects were observed at AP dosage levels < or = 1.0 mg/kg/day. In the absence of thyroid organ weight and histopathological effects, the toxicological significance of TSH and thyroid hormone changes at AP dosage levels < or = 1.0 mg/kg/day remains to be determined.     

A possible mechanism for decrease in serum thyroxine level by polychlorinated biphenyls in Wistar and Gunn rats.

We have previously demonstrated that in mice, the decrease in serum thyroxine (T(4)) level by polychlorinated biphenyls (PCBs) occurs without an increase in the UDP-glucuronosyltransferase (T(4)-UDP-GT) for T(4) glucuronidation, although the PCB-induced decrease in rats is generally thought to occur through induction of T(4)-UDP-GT, UGT1A1, and UGT1A6. In the present study, to further clarify the relationship between the decrease in serum T(4) level and the increase in UGT1A activity by PCB in rats, we examined the relationship using Wistar rats and Gunn rats, a mutant strain of Wistar rats deficient in UGT1A isoforms. The serum total T(4) level was markedly decreased not only in the Wistar rats but also in the Gunn rats 4 days after treatment with a PCB, Kanechlor-500 (KC500, 100 mg/kg) or 2,2',4,5,5'-pentachlorobiphenyl (PentaCB, 112 mg/kg), and there was no significant difference in magnitude of the decrease between the two rat strains. At the same time, the level and activity of T(4)-UDP-GT were significantly increased by treatment with either KC500 or PentaCB in Wistar rats but not in Gunn rats. In addition, no significant change in the level of serum total triiodothyronine (T(3)) and thyroid-stimulating hormone by the KC500 treatment was observed in either Wistar or Gunn rats. Furthermore, significant decrease in the activity of hepatic type-I deiodinase, which mediates the deiodization of T(4) and T(3), by treatment with KC500 or PentaCB was observed in both Wistar and Gunn rats. From the serum of KC500- or PentaCB-treated Wistar and Gunn rats, mono- and di-hydroxylated PCB metabolites, which would bind to T(4) binding serum protein (transthyretin), were detected. In conclusion, the present results suggest that the decrease in serum total T(4) level by either KC500 or PentaCB in Gunn rats was not dependent on the increase in hepatic T(4)-UDP-GT activity. The findings further suggest that the PCB-mediated decrease in serum T(4) level might occur, at least in part, through formation of the hydroxylated PCB metabolites. Furthermore, even in Wistar rats, the PCB-mediated decrease in serum T(4) level might occur not only through the increase in hepatic T(4)-UDP-GT but also via formation of hydroxylated PCB metabolites.     

Altered expression of the Olr59, Ethe1, and Slc10a2 genes in the liver of F344 rats by neonatal thyroid hormone disruption

Many concerns have been expressed regarding the possible adverse effects of thyroid hormone‐disrupting chemicals in the environment. The disruption of thyroid hormones in the neonatal period may lead to permanent effects on thyroid hormone homeostasis as well as related developmental disorders, as thyroid hormones are essential for regulating the growth and differentiation of many tissues. To understand the long‐term alteration in gene expressions by neonatal administration of thyroid hormone‐like chemicals in general, we identified genes whose expression was altered in the liver, an important component of the thyroid hormone axis, by neonatal exposure to triiodothyronine (T3). T3 was administered to male F344 rats on postnatal days 1, 3, and 5 (week 0). At 8 weeks of age, cDNA microarray analysis was used to identify hepatic genes whose expression was altered by neonatal exposure to T3. Among the up‐regulated genes that were identified, the expression of Olr59 , Ethe1 , and Slc10a2 increased specifically in rats neonatally exposed to T3. Interestingly, altered hepatic expression of these genes indeed increased when a hydroxylated polybrominated diphenyl ether (PBDE), OH‐BDE42, which is capable of binding to the TR, was given neonatally. Our data demonstrated that neonatal exposure to thyroid hormones could affect the long‐term expression of the genes, which could be useful markers for neonatal effects by thyroid hormone‐disrupting chemicals. Copyright © 2017 John Wiley & Sons, Ltd.     

A 28-day oral (dietary) toxicity study of sucromalt in Sprague--Dawley rats.

A new sweetener, sucromalt, was produced via enzymatic conversion of sucrose and maltose to a mixture of fructose, leucrose and gluco-oligosaccharides. The present study evaluated the safety of this sweetener when administered as a dietary admix at concentrations of 50, 100 and 200 g/kg to Sprague-Dawley rats for 28 days. There were no treatment-related effects on the general condition and behavior as determined by clinical observations, functional observational battery and locomotor activity assessments. Evaluation of clinical pathology parameters revealed no toxicologically-relevant treatment-related effects on hematology, serum chemistry or urinalysis. Macroscopic and microscopic findings revealed no treatment-related effects on any organ evaluated. A treatment-related increase in mean food consumption was observed resulting in slightly higher body weight gains (2-4%) for both the male and female rats, which was not toxicologically relevant. Results of this study clearly demonstrate that consumption of high concentrations of sucromalt for 28 days is not associated with obvious signs of toxicity.     

17alpha-methyltestosterone: 28-day oral toxicity study in the rat based on the "Enhanced OECD Test Guideline 407" to detect endocrine effects

A 28-day oral gavage toxicity study in the rat with 17alpha-methyltestosterone was conducted as part of the international validation exercise on the modified Enhanced OECD Test Guideline 407 (Organisation for Economic Co-operation and Development, Paris). Special emphasis was placed on the endocrine mediated effects exerted by 17alpha-methyltestosterone, a potent androgen agonist. The test compound was administered daily by oral gavage for at least 28 days to groups of 7-week-old-Wistar rats. Dose levels were 0, 10, 40 and 200 mg/kg body weight per day for males and 0, 10, 100 and 600 mg/kg body weight per day for females. In addition, and outside the remit of the enhanced protocol, testosterone levels in males, oestradiol levels in females and luteinizing hormone (LH) levels in both sexes were measured, to provide a broader profile on the hormonally mediated effects of 17alpha-methyltestosterone. Furthermore, stage-specific quantification of Terminal deoxynucleotidyl transferase-mediated dUTP Nick-End Labeling (TUNEL)-labeled germ cells (apoptotic germ cells) in the seminiferous tubules was also performed, in an effort to demonstrate the precise stages in the spermatogenic cycle 17alpha-methyltestosterone exerts its effect. In this study, the most critical additional parameters contained in the Enhanced OECD Test Guideline 407 for the detection of endocrine disruption were considered to be the histopathological assessment and organ weight data of endocrine-related tissues. Beyond the scope of this validation exercise, an increase in apoptosis in specific germ cell types was detected using the TUNEL assay in male rats treated at 200 and 40 mg/kg.     

Mechanisms of Endocrine Disruption with Particular Reference to Occurrence in Avian Wildlife: A Review

This review examines the evidence for endocrine disruption in birds. It reviews in vitro and in vivo laboratory based evidence for endocrine disruption by (1) agonism or antagonism of gonadal steroid hormones, (2) altering the activity of cytochrome P450 enzymes, (3) altering thyroid hormone function, (4) affecting intrinsic neuroendocrine control mechanisms and (5) activation of the stress response. It also discusses the evidence for the existence of such effects in free-living birds. In vitro studies demonstrate that mechanisms for potential endocrine disruption exist, but in vivo studies suggest that such mechanisms are insufficient to overwhelm endogenous homeostatic control. There are only two phenomena in wild birds where endocrine disruption has been cited as a possible cause: eggshell thinning and supernormal clutches. Evidence suggests that neither of these is caused by endocrine disruption. Despite three decades of concern, there is no evidence that avian wildlife has suffered endocrine disruption.     

Effects of the brominated flame retardant hexabromocyclododecane (HBCD) on dopamine-dependent behavior and brainstem auditory evoked potentials in a one-generation reproduction study in Wistar rats

Hexabromocyclododecane (HBCD) is a widely used brominated flame retardant which has been recently detected in many environmental matrices. Data from a subacute toxicity study indicated dose-related effects particularly on the pituitary thyroid-axis and retinoids in female rats. Brominated and chlorinated aromatic hydrocarbons are also reported to exert effects on the nervous system. Several investigations revealed a pronounced sensitivity of the dopaminergic system and auditory functions to polychlorinated biphenyls. Therefore, the present experiment should examine, whether or not HBCD affects these targets. Rats were exposed to 0, 0.1, 0.3, 1, 3, 10, 30 or 100 mg HBCD/kg body weight via the diet. Exposure started before mating and was continued during mating, gestation, lactation, and after weaning in offspring. Haloperidol-induced catalepsy and brainstem auditory evoked potentials (BAEPs) were used to assess dopamine-dependent behavior and hearing function in adult male and female offspring. On the catalepsy test, reduced latencies to movement onset were observed mainly in female offspring, indicating influences on dopamine-dependent behavior. The overall pattern of BAEP alterations, with increased thresholds and prolonged latencies of early waves, suggested a predominant cochlear effect. Effects were dose-dependent with lower bounds of benchmark doses (BMDL) between ≤1 and 10 mg/kg body weight for both catalepsy and BAEP thresholds. Tissue concentrations at the BMDL values obtained in this study were 3–4 orders of magnitude higher than current exposure levels in humans.     

Evaluation of the toxicity of concentrated barley beta-glucan in a 28-day feeding study in Wistar rats.

Beta-glucans are water-soluble cell-wall polysaccharides consisting of (1-->3,1-->4)-linked beta-D-glucopyranosyl monomers that comprise a considerable proportion of soluble fiber from certain grains including oats and barley. Consumption of foods containing beta-glucan or beta-glucan-enriched fractions prepared from these grains lower serum cholesterol concentrations in humans and in animal models of hypercholesterolemia. The present study was conducted to evaluate the toxicity of beta-glucan-enriched soluble fiber from barley in Wistar rats on dietary administration at concentrations of 0.7, 3.5 and 7% beta-glucan for 28 days. There were no adverse effects on general condition and behavior, growth, feed and water consumption, feed conversion efficiency, red blood cell and clotting potential parameters, clinical chemistry values, and organ weights. Necropsy and histopathology findings revealed no treatment-related changes in any organ evaluated. A dose-dependent increase in full and empty cecum weight was observed. This is a common physiological response of rodents to high amounts of poorly digestible, fermentable carbohydrates, and was of no toxicological concern. The only finding of possible biological relevance was an increase in the number of circulating lymphocytes observed in males. However, the increase was not dose-dependent and was not observed in females. Results of this study demonstrated that consumption of concentrated barley beta-glucan was not associated with any obvious signs of toxicity in Wistar rats even following consumption of large quantities.     

Exposure to tetrabromobisphenol A (TBBPA) in Wistar rats: neurobehavioral effects in offspring from a one-generation reproduction study

Within the framework of an EU project on risk assessment of brominated flame retardants, TBBPA was studied for neurobehavioral effects in rats. To permit benchmark dose analysis, eight dose levels were chosen ranging from 0 to 3000mg/kg body weight. Exposure of parental rats started 10 and 2 weeks before mating in males and females, respectively, and was continued throughout mating, gestation and lactation. After weaning, exposure was continued in the offspring throughout life. Previous studies had indicated TBBPA-induced effects on thyroid hormones. Because of the known implication of thyroid hormones in neurodevelopment, the present experiments tested if TBBPA exposure affects thyroid-dependent neurobehavioral functions in offspring, such as auditory responses and conditioned fear. Sweet preference was included because of sex-specific effects in littermates. No statistically significant effects were found on context or cue conditioned fear or sweet preference. Auditory responses were examined with brainstem auditory evoked potentials (BAEPs) at approximately 50-110 days of age. BAEP thresholds and wave IV latency were increased in exposed female rats in the low frequency range. In male rats, thresholds were unaffected, but absolute latency of wave IV and interpeak latencies II-IV showed exposure-related increases at low frequencies. The outcome pattern suggests a predominant cochlear effect of TBBPA in females while in males neural effects are more apparent. According to benchmark analysis, the critical effect doses (CED) for prolongations of wave IV latency at 0.5kHz were in the range of 35-70mg/kg body weight with lower bounds (BMDL) of approximately 8mg/kg in males and females. The BMDL values for elevation of hearing thresholds in females were in the range of 1-40mg/kg body weight, depending on frequency. The benchmark doses for effects on the BAEP were similar to values for decreases in circulating thyroid hormones. The comparison of the exposure level at which the most sensitive effect was found with current human exposure levels yielded a margin of exposure of about 5, according to a recent risk assessment. Further investigations are needed to examine exposure pathways, fate in the body and effects of TBBPA.     

Twenty-eight days repeated oral dose toxicity study of gemifloxacin in Wistar albino rats

The purpose of this study was to investigate the potential toxicity of gemifloxacin by 28-day repeated oral dose in Wistar albino rats. The test article, was administered daily by gavage to male and female rats at dose levels of 0, 50, 100, 200 mg/kg/day. At the end of treatment period, 12 rats/sex/group was sacrificed, while six extra rats/sex in the vehicle control and highest dose groups sacrificed after 14 days recovery period. During the treatment and recovery periods, clinical signs, mortality, body weights, food and water consumption, ophthalmoscopy, urinalysis, phototoxicity, hematology, serum biochemistry, synovial fluid biochemistry, electrocardiogram (ECG), gross findings, organ weights, microscopic examination of synovial fluid, and histopathology were examined. Hematological and serum biochemical investigations revealed a dose-dependent increase in the total white blood cell (WBC), total bilirubin (T-BIL), glucose (GLU), alanine aminotransferase (ALT) and significant decreases in total protein (TP) were observed in both sexes at the same dose, at the end of treatment period, but the levels returned toward normal during the recovery period. Histopathology of talar joint showed that erosion of the articular surface of that joint in both sexes at the end of treatment period at the dose level of 200 mg/kg/day. Degenerative changes in tendinocytes were observed in Achilles tendon of both sexes at the high dose level at the end of treatment period. In histopathological study shows partial effacement of liver architecture and focal ulceration in gastric mucosa at the high dose level at the end of treatment period. Based on these results, it was concluded that 28 days repeated oral dose of gemifloxacin caused increases in the liver weight, WBC count, T-BIL, glucose level, ALT, decreasing the TP, cause chronic hepatitis and acute gastritis, erosion of the articular surface of joint and histopathologic changes in Achilles tendon in rats at the dose level of 200 mg/kg/day.