Effects of intermediate frequency magnetic fields on male fertility indicators in mice.

Human exposure to intermediate frequency (IF) fields is increasing due to new applications such as electronic article surveillance systems, wireless power transfer and induction heating cookers. However, limited data is available on effects of IF magnetic fields (MF) on male fertility function. This study was conducted to assess possible effects on fertility indicators from exposure to IF MF. Male C57BL/6J mice were exposed continuously for 5 weeks to 7.5kHz MF at 12 and 120µT. Sperm cells from cauda epididymis were analysed for motility, total sperm counts, and head abnormalities. Motile sperm cells were classified as progressive or non-progressive. Testicular spermatid heads were counted as well. The body weight development and reproductive tissue weights were not affected. No exposure-related differences were observed in sperm counts or sperm head abnormalities. Proportion of non-motile cells was significantly decreased in the 120µT group, and a corresponding increase was seen in the percentage of motile cells (significant in non-progressive motile cells). In conclusion, no adverse effects on fertility indicators were observed. Increased sperm motility is an interesting finding that needs to be confirmed in further studies.

Synergistic proinflammatory interactions of microbial toxins and structural components characteristic to moisture-damaged buildings.

Indoor exposure to microbes and their structural and metabolic compounds is notoriously complex. To study proinflammatory interactions between the multiple microbial agents, macrophages derived from human THP-1 monocytic cells were exposed to several concentrations of microbial toxins alone (emodin, enniatin B, physcion, sterigmatocystin, valinomycin) and in combination with microbial structural components (bacterial lipopolysaccharide [LPS] or fungal ß-glucan). While the expression of proinflammatory cytokines TNFα and IL-1ß to single toxins alone was modest, low-dose co-exposure with structural components increased the responses of emodin, enniatin B, and valinomycin synergistically, both at the mRNA and protein level, as measured by RT-qPCR and ELISA, respectively. Co-exposure of toxins and ß-glucan resulted in consistent synergistically increased expression of several inflammation-related genes, while some of the responses with LPS were also inhibitory. Co-exposure of toxins with either ß-glucan or LPS induced also mitochondrial damage and autophagocytosis. The results demonstrate that microbial toxins together with bacterial and fungal structural components characteristic to moisture-damaged buildings can have drastic synergistic proinflammatory interactions at low exposure levels.

Effects of developmental exposure to perfluorooctanoic acid (PFOA) on long bone morphology and bone cell differentiation.

Perfluorooctanoic acid (PFOA) is a ubiquitous and persistent environmental chemical, which has been used extensively due to its stability and surface tension-lowering properties. Toxicological effects include induction of neonatal mortality and reproductive toxicity. In this study, pregnant C57BL/6 mice were exposed orally to 0.3mg PFOA/kg/day throughout pregnancy, and female offspring were studied at the age of 13 or 17months. Morphometrical and biomechanical properties of femurs and tibias were analyzed with micro-computed tomography and 3-point bending, and bone PFOA concentrations were determined by mass spectrometry. The effects of PFOA on bone cell differentiation were studied in osteoclasts from C57BL/6 mice and in the MC3T3 pre-osteoblast cell line. PFOA exposed mice showed increased femoral periosteal area as well as decreased mineral density of tibias. Biomechanical properties of these bones were not affected. Bone PFOA concentrations were clearly elevated even at the age of 17months. In osteoblasts, low concentrations of PFOA increased osteocalcin (OCN) expression and calcium secretion, but at PFOA concentrations of 100µM and above osteocalcin (OCN) expression and calcium secretion were decreased. The number of osteoclasts was increased at all PFOA concentrations tested and resorption activity dose-dependently increased from 0.1-1.0µM, but decreased at higher concentrations. The results show that PFOA accumulates in bone and is present in bones until the old age. PFOA has the potential to influence bone turnover over a long period of time. Therefore bone is a target tissue for PFOA, and altered bone geometry and mineral density seem to persist throughout the life of the animal.

Associations between congenital cryptorchidism in newborn boys and levels of dioxins and PCBs in placenta.

In animal studies, exposure to dioxins has been associated with disrupted development of the male reproductive system, including testicular maldescent. Some polychlorinated biphenyls (PCBs) have also dioxin-like effects. In addition, one previous case-control study has reported an association between congenital cryptorchidism and colostrum PCB levels. We performed a case-control study to evaluate whether congenital cryptorchidism in boys was associated with increased levels of dioxins or PCBs in placenta reflecting foetal exposure. In addition, associations between placenta levels of these chemicals and reproductive hormone levels in boys at 3 months were studied. Placentas were collected in a Danish-Finnish joint prospective cohort study on cryptorchidism (1997-2001). The boys were examined for cryptorchidism at birth and at 3 months. Altogether, 280 placentas [112 Finnish (56 cases, 56 controls) and 168 Danish (39 cases, 129 controls)] were analysed for 17 toxic polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and 37 PCBs (including 12 dioxin-like PCBs). Infant serum samples taken at 3 months were analysed for reproductive hormones. No significant differences between cases and controls were observed in either country in dioxin WHO-TEq levels (median 9.78 vs. 8.47 pg/g fat, respectively, in Finland, and 11.75 vs. 10.88 pg/g fat in Denmark) or PCB WHO-TEq levels (median 2.12 vs. 2.15 pg/g fat in Finland, 2.34 vs. 2.10 pg/g fat in Denmark) or total-TEq levels (median 11.66 vs. 10.58 pg/g fat in Finland, 13.94 vs. 13.00 pg/g fat in Denmark). Placenta WHO-TEq levels of dioxins were not associated with infant reproductive hormone levels at 3 months. In Finland, PCB WHO-TEq levels in placenta associated positively with infant LH levels. WHO-TEq levels of dioxins and PCBs and total-TEq levels were higher in Danish than Finnish samples. In conclusion, no association between placenta levels of dioxins or PCBs and congenital cryptorchidism was found. Significant country differences in chemical levels were observed.

The effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on foetal male rat steroidogenesis.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is the most toxic and widely investigated dioxin congener. In utero and lactational exposure to TCDD results in developmental and reproductive defects that are the most sensitive endpoints for TCDD toxicity. TCDD has a potential to interfere with steroid metabolism, but the mechanisms by which this occurs are not well understood. In this study, we investigated the effects of TCDD on prenatal rat steroidogenesis. Pregnant Sprague-Dawley female rats were treated once with TCDD (0, 0.3 or 1 microg/kg) by gavage on embryonic day (ED) 11 and the expression levels of androgen (AR) and estrogen receptors (ER), steroidogenic enzymes (P450scc and 3beta-HSD) and four regulatory factors (StAR, SF-1, GATA-4 and Insl-3) involved in foetal Leydig cell and adrenal function were analysed on ED 19.5. Hormonal status of male foetuses was determined by measuring testicular testosterone (T) levels, plasma luteinizing hormone (LH) and corticosterone concentrations. In utero exposure to TCDD reduced intratesticular T of foetal males (significant at 0.3 microg/kg TCDD) and tended to reduce the protein expression of ERalpha and AR of foetal male rat testis. Foetal male rat plasma LH levels were significantly reduced at the dose of 1 microg/kg TCDD, while corticosterone levels tended to be increased possibly because of the TCDD-induced stress. Only minor alterations in steroidogenesis were observed in rat adrenal. mRNA expression of developmental regulatory factors was not influenced by foetal TCDD exposure, except for significantly reduced adrenal SF-1. The results demonstrate that maternal exposure to TCDD suppressed testicular steroidogenesis of 19.5-day-old foetal male Sprague-Dawley rat. The highest dose of TCDD (1 microg/kg) had also an effect on pituitary LH secretion. Our data implicate that TCDD has direct testicular and pituitary effects on foetal male rat but with different dose-responses. These changes can lead to impaired steroidogenesis and it may result in the maldevelopment of the testis and weaken masculinization.

Perfluoroalkyl substances in human bone: concentrations in bones and effects on bone cell differentiation.

Perfluoroalkyl substances (PFAS), including two most commonly studied compounds perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), are widely distributed environmental pollutants, used extensively earlier. Due to their toxicological effects the use of PFAS is now regulated. Based on earlier studies on PFOA's distribution in bone and bone marrow in mice, we investigated PFAS levels and their possible link to bone microarchitecture of human femoral bone samples (n = 18). Soft tissue and bone biopsies were also taken from a 49-year old female cadaver for PFAS analyses. We also studied how PFOA exposure affects differentiation of human osteoblasts and osteoclasts. PFAS were detectable from all dry bone and bone marrow samples, PFOS and PFOA being the most prominent. In cadaver biopsies, lungs and liver contained the highest concentrations of PFAS, whereas PFAS were absent in bone marrow. Perfluorononanoic acid (PFNA) was present in the bones, PFOA and PFOS were absent. In vitro results showed no disturbance in osteogenic differentiation after PFOA exposure, but in osteoclasts, lower concentrations led to increased resorption, which eventually dropped to zero after increase in PFOA concentration. In conclusion, PFAS are present in bone and have the potential to affect human bone cells partly at environmentally relevant concentrations.

Liver tumor-promoting activity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in TCDD-sensitive and TCDD-resistant rat strains.

Risk assessment of dioxins is currently based on induction of liver tumors in rats. The toxicity of dioxins is characterized by large sensitivity differences among animal species and even strains of the same species, which complicates the risk assessment. The significance of these differences in dioxin-induced carcinogenicity is not known. We therefore studied the liver tumor-promoting activity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the sensitive Long-Evans (L-E) and the resistant Han/Wistar (H/W) rats differing >1000-fold in their sensitivity to the acute lethaity of TCDD. Female rats were partially hepatectomized, initiated with nitrosodiethylamine, and treated with TCDD for 20 weeks. Altered hepatic foci (AHF) were stereologically quantitated using glutathione S-transferase P as a marker. AHF were significantly (P < 0.001) and dose dependently increased in L-E rats at 10 and 100 ng/kg/day, but in H/W rats only at 1000 ng/kg/day and above, indicating a remarkable (approximately 100-fold) sensitivity difference between L-E and H/W rats. The same sensitivity difference but 10-fold less foci were observed between nonhepatectomized/noninitiated L-E and H/W rats. Induction of AHF was related to hepatotoxicity but not to cytochrome P4501A1 activity in the liver. Liver TCDD concentrations were similar in both strains. H/W rats are exceptionally resistant to induction of AHF by TCDD, and the resistance is associated with an altered transactivation domain of the aryl hydrocarbon receptor. Genetic differences may account for significant interindividual/intraspecies sensitivity differences in dioxin-induced carcinogenesis. Understanding the role of transactivation domain of the aryl hydrocarbon receptor in carcinogenesis is therefore likely to improve dioxin risk assessment.

Biomonitoring of selected persistent organic pollutants (PCDD/Fs, PCBs and PBDEs) in Finnish and Russian terrestrial and aquatic animal species.

BACKGROUND: The Finnish and Russian animal species (semi-domesticated reindeer, Finnish wild moose, Baltic grey seal and Baltic herring) samples were biomonitored in terrestrial and aquatic environments for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs) and polybrominated diphenylethers (PBDEs). RESULTS: Grey seal (Halichoerus grypus) was clearly the most contaminated species. The mean PBDE concentration in grey seal was 115 ng/g fat, and the highest WHO-PCDD/F-PCB-TEQ (toxic equivalent set by WHO) was 327 pg/g fat. In Finnish, reindeer WHO-PCDD/F-TEQ varied from 0.92 pg/g fat in muscle to 90.8 pg/g fat in liver. WHO-PCDD/F-TEQ in moose liver samples was in the range of 0.7-4.26 pg/g fat, and WHO-PCB-TEQ in the range of 0.42-3.34 pg/g fat. Overall moose had clearly lower PCDD/F and DL-PCB concentrations in their liver than reindeer. CONCLUSIONS: Terrestrial animals generally had low POP concentrations, but in reindeer liver dioxin levels were quite high. All Finnish and Russian reindeer liver samples exceeded the EU maximum level [8] for PCDD/Fs (10 pg/g fat), which is currently set for bovine animals.

In utero and lactational exposure to TCDD; steroidogenic outcomes differ in male and female rat pups.

TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) has a potency to induce decreased fertility and structural reproductive anomalies in male and female mammals. While the activity profile of sex steroid hormone production distinctly differs in developing males and females, we wanted to analyze sex-specific effects of TCDD introduced in utero and via lactation on gonadal steroidogenesis and gonadotropin levels in male and female rat infant pups. One oral dose of TCDD (0, 0.04, 0.2, or 1.0 microg/kg) was given to dams on gestational day (GD) 13. Plasma testosterone, estradiol, progesterone, follicle stimulating hormone (FSH), luteinizing hormone (LH), and gonadal mRNA levels for steroid acute regulatory protein (StAR), cytochrome P-450 cholesterol side-chain cleavage (P450scc), 3beta-hydroxy-steroid-dehydrogenase/Delta(5)-Delta(4) isomerase type I (3beta-HSD1), P-450 17alpha-hydroxylase/17,20-lyase (P450-17alpha), and cytochrome P-450 aromatase (P450arom) were determined on postnatal days (PND) 10-16. TCDD 1.0 mug/kg reduced body weights but did not affect relative testis weight or alter testicular and ovarian histology. Plasma estradiol levels in dams and female pups were reduced on PND 14 and 16. Progesterone levels remained unaltered, and FSH levels were increased in female pups. In males, testosterone levels were elevated on PND 10. Gonadal mRNA levels for StAR and steroidogenic enzymes increased during the postnatal growth. TCDD caused no changes in relatively low testicular mRNA levels. However, significant reductions in StAR and P450arom mRNA levels were seen in PND 14 ovaries, and P450arom activity was decreased in isolated ovarian follicles. We conclude that developing testis and male gonadotropin secretion are resistant to TCDD-induced toxicity. In female pups, reduced estradiol, ovarian P450arom expression and enzyme activity levels, and elevated FSH levels may have a role in the development of ovarian dysfunction reported in TCDD-exposed females.

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on bone in two rat strains with different aryl hydrocarbon receptor structures.

Polychlorinated dibenzo-p-dioxins (PCDDs) are highly toxic environmental contaminants, and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is the most potent dioxin. Here, we studied the effects of TCDD on bone. Two rat strains, Han/Wistar (H/W) and Long-Evans (L-E), were used because they exhibit a 1000-fold sensitivity difference in acute lethality of TCDD, which difference is related to the aryl hydrocarbon receptor (AHR). TCDD inhibited the tibial growth dose dependently, the effect being manifested at lower doses in the more sensitive L-E strain. In H/W rats the effect of TCDD was seen only at the high dose of 170 microg/kg (p < 0.05), whereas in the sensitive L-E rats a significant reduction of bone growth was already seen at 1.7 microg/kg (p < 0.01). This reduction was caused by the smaller tibial size because the diaphyseal bone mineral density (BMD) did not change. The three-point bending breaking force of the tibia was significantly reduced in H/W rats at 170 microg/kg (p < 0.05), but tibial stiffness was lower already at the dose of 17 microg/kg (p < 0.05). In the sensitive L-E strain, both breaking force and stiffness were reduced at the dose of 17 microg/kg (p < 0.001). These results indicate that TCDD dose-dependently interferes with bone growth, modeling, and mechanical strength. The altered transactivation domain of AHR is associated with a lower sensitivity of bone to TCDD in H/W rats, suggesting that AHR plays a role in modulating the effects of dioxins on bone.

Polybrominated diphenyl ethers: occurrence, dietary exposure, and toxicology.

Polybrominated diphenyl ethers (PBDEs) are used as flame retardants in plastics (concentration, 5--30%) and in textile coatings. Commercial products consist predominantly of penta-, octa-, and decabromodiphenyl ether mixtures, and global PBDE production is about 40,000 tons per year. PBDEs are bioaccumulated and biomagnified in the environment, and comparatively high levels are often found in aquatic biotopes from different parts of the world. During the mid-1970--1980s there was a substantial increase in the PBDE levels with time in both sediments and aquatic biota, whereas the latest Swedish data (pike and guillemot egg) may indicate that levels are at steady state or are decreasing. However, exponentially increasing PBDE levels have been observed in mother's milk during 1972--1997. Based on levels in food from 1999, the dietary intake of PBDE in Sweden has been estimated to be 0.05 microg per day. Characteristic end points of animal toxicity are hepatotoxicity, embryotoxicity, and thyroid effects as well as maternal toxicity during gestation. Recently, behavioral effects have been observed in mice on administration of PBDEs during a critical period after birth. Based on the critical effects reported in available studies, we consider the lowest-observed-adverse-effect level (LOAEL) value of the PBDE group to be 1 mg/kg/day (primarily based on effects of pentaBDEs). In conclusion, with the scientific knowledge of today and based on Nordic intake data, the possible consumer health risk from PBDEs appears limited, as a factor of over 10(6) separates the estimated present mean dietary intake from the suggested LOAEL value. However, the presence of many and important data gaps, including those in carcinogenicity, reproduction, and developmental toxicity, as well as additional routes of exposure, make this conclusion only preliminary. Moreover, the time trend of PBDEs in human breast milk is alarming for the future.

Decreased liver type I 5'-deiodinase and increased brown adipose tissue type II 5'-deiodinase activity in 2,3,7,8-tetrachlorobibenzo-p-dioxin (TCDD)-treated Long-Evans rats.

The effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was studied on the activity of type I 5'-deiodinase (5' DI) in liver and of type II 5'-deiodinase (5' DII) in brown adipose tissue (BAT) microsomes of Long-Evans rats. TCDD decreased the activity of liver 5' DI and increased that of BAT 5' DII. It also reduced the concentration of serum total thyroxine (T4) without affecting triiodothyronine (T3). These effects of TCDD on 5'-deiodinases and serum thyroid hormones are compatible with partial hypothyroidism. Based on our results, it is not possible to decide unequivocally whether TCDD affects thyroid hormone status and 5'-deiodination by a direct action or a feedback mechanism. However, these data are important because they demonstrate that TCDD affects thyroid status in a tissue-specific manner and that its effects on thyroid hormone metabolism are much more complex than currently assumed.

Cytokines (IL-1beta and TNFalpha) in relation to biochemical and immunological effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in rats.

Previous studies in different strains of rats and mice have shown that the inhibition of gluconeogenesis as a result of reduced liver phosphoenolpyruvate carboxykinase (PEPCK) activity together with appetite suppression play critical roles in the acute toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Recent immunological studies in rats demonstrated that exposure to low doses of TCDD resulted in an early and enhanced IgG response to immunization with sheep red blood cells (SRBC) and an enhanced delayed-type hypersensitivity (DTH) reaction as well as a positive popliteal lymph node (PLN) response. However, high doses of TCDD suppressed the DTH reaction. This study aimed at examining the involvement of cytokines (IL-1 and TNF) in mediating the above effects. Liver samples from a previous dose-response study on DTH reaction were investigated, in which rats were treated with TCDD (1, 3, 10, 30 and 90 microg/kg) and immunized with an antigen. mRNA levels of IL-1beta were elevated begining at the 1 microg/kg (non-lethal) dosage group with a maximum increase of about 5-fold above controls in the 90 microg/kg (lethal) dosage group. mRNA levels of TNFalpha were also significantly elevated begining at the 30 microg/kg dosage group. These results suggest that at low doses of TCDD, increased IL-1beta could be responsible for immune function stimulation, whereas at high doses of TCDD, greatly elevated TNFalpha and IL-1beta levles may exacerbate or mediate acute toxicity including immune suppression and related biochemical effects. A time course study (60 microg TCDD/kg without immunization) revealed that liver mRNA levels of TNFalpha were significantly elevated starting 24 h, and reaching a maximum 48 h after dosing with TCDD. This change was accompanied by a transient increase of mRNA levels of IL-1beta at day 4 after TCDD dosage. Thus, these data demonstrated that TCDD alone (without immunization) can cause transient increases of mRNA levels of TNFalpha and IL-1beta in liver. Results from these experiments suggest that TCDD-induced cytokine changes may play important roles in various effects of TCDD.

Characteristics and modulation of dithranol (anthralin)-induced skin irritation in the mouse ear model.

Dithranol-induced skin irritation and the modulatory effects of different pharmacological agents were studied using the mouse ear model. A single topical application of dithranol caused a dose-dependent skin irritation which resulted in delayed swelling of the mouse ear with two separate peak responses, 1-2 and 6-10 days after application. The irritation was most effectively and persistently inhibited by topical treatment with corticosteroids, the free radical scavenger DL-alpha-tocopherol (DLAT) and the serotonin antagonist metergoline. The effect of corticosteroids, however, was slightly diminished during the second peak irritation. The lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA), the dual lipoxygenase and cyclo-oxygenase inhibitor tolfenamic acid and the cyclo-oxygenase inhibitor indomethacin as well as trifluoperazine retained their inhibitory activity. Of these compounds, indomethacin was active only during the first irritation peak, NDGA during both peaks and trifluoperazine principally during the second peak. Retinoic acid did not inhibit the ear swelling. The results confirm and extend the observations that the formation of free radicals is essential for dithranol inflammation. The inflammation can also be suppressed by inhibiting the formation of arachidonic acid or its pro-inflammatory metabolites.

Changes in food intake and food selection in rats after 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) exposure.

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on food selection were studied in TCDD-resistant Han/Wistar and TCDD-sensitive Long-Evans rats and their crosses. The rats were offered a selection diet consisting of chocolate, cheese, and chow, and TCDD was given at the same time or 4 or 16 days later. TCDD persistently reduced the chocolate intake. When the selection diet was started at the time of or less than 11 h after TCDD exposure, TCDD almost completely prevented the intake of chocolate and also cheese in all strains already on the first day, while controls started to consume large amounts of both foods. This may be due to conditioned taste aversion. The effect on food selection with familiar foods seemed to reduce fat intake, while protein and carbohydrate intakes were more variable. There were no major strain differences in the chocolate intake inhibition despite a 1000-fold sensitivity difference in TCDD lethality.

Comparison of acute toxicities of indolo[3,2-b]carbazole (ICZ) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in TCDD-sensitive rats.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and related halogenated aromatic hydrocarbons are environmental toxicants that act via the AH receptor (AHR). In vitro studies have demonstrated that some indole derivatives present in cruciferous vegetables also bind to the AHR. One of the highest AHR binding affinities is exhibited by indolo[3,2-b]carbazole (ICZ). Since exposure to these dietary indoles is quantitatively far larger than that to halogenated aromatic compounds, their potential toxic risks have raised concern. In the present study, we compared the effects of ICZ with those of a single dose of 20 microg/kg TCDD in the most TCDD-sensitive rat strain (Long-Evans [Turku AB]) (L-E). Whereas TCDD elicited the expected toxicity syndrome, ICZ, either as a single subcutaneous dose (63.5, 127 or 508 microg/kg) or with repeated sc dosing (508 microg/kg for 5 days) failed to reproduce any toxic impacts of TCDD. Furthermore, a simultaneous ICZ treatment (63.5 or 127 microg/kg for 10 days) did not interfere with TCDD (20 microg/kg; single exposure) action. A moderate hepatic induction of CYP1A1 could be triggered by repeated intragastric administration of ICZ (127 microg/kg for 4 days, the last treatment 2.5 h prior to termination). In control experiments in a reconstituted yeast system, ICZ potently and dose-dependently activated L-E rat AHR function demonstrating that it represents a bona fide high-affinity ligand for the rat receptor in vivo. Thus, the present study does not support the view that dietary exposure to ICZ would present a hazard of AHR-mediated adverse health effects to humans.

Subchronic (13-week) toxicity of heptachlorodibenzo-p-dioxin in male Sprague-Dawley rats.

A 13-week oral toxicity study with 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (HpCDD) was performed in Sprague-Dawley rats. Rats received HpCDD at five different dose levels or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) at one dose level. The doses were divided into 4 daily loading doses and 6 biweekly maintenance doses. At the end of the 13-week dosing period half of the rats were scheduled for necropsy and the other half after another 13-week off-dose period. This preliminary report contains only data from male rats during the 13-week main study period. At the two highest doses of HpCDD and in the TCDD dosage group the body weight or body weight gain was reduced. Mortality was 15, 50 and 5%, respectively. Wasting syndrome was the primary cause of death, but some rats died of hemorrhage without wasting, which may be related to the dose-dependent decrease in platelet counts. Phosphoenolpyruvate carboxykinase (PEPCK), the rate limiting enzyme of gluconeogenesis, was decreased only at the two highest dose levels of HpCDD and in the TCDD group, all of which also showed mortality. Ethoxyresorufin O-deetylase (EROD) was induced dose-dependently in all treated groups. Serum total thyroxine (T4) concentrations were decreased beginning at the middle dose of HpCDD. The study demonstrates that the toxicity observed after subchronic exposure to HpCDD is very similar to that of TCDD. Most importantly, most of the effects after subchronic and acute dose exposure are identical, confirming the validity of 0.007 as the toxic equivalency factor for HpCDD.

Absorption of various erythromycin esters and salts in mice after intragastric intubation.

Erythromycin base and its different salts and esters were given intragastrically to mice. Serum concentrations of erythromycin and its 2'-esters were determined by the bacterial growth inhibition method. Acetyl and propionyl erythromycin were the best absorbed 2'-esters, and differed significantly from butyryl erythromycin and erythromycin base. Erythromycin estolate yielded a larger area under the concentration curve than acistrate or stearate. Among the syrup preparations, erythromycin acistrate was significantly better absorbed than 2'-ethylsuccinyl erythromycin. Absorption of 2'-esters decreased with increasing number of esterified carbon atoms and increasing hydrophobicity and increasing log P value (the logarithm of octanol-water partition coefficient). In addition to sufficient lipophilicity, the optimum absorption of erythromycin esters seems to require a high hydrophilicity.

Differences in binding of epidermal growth factor to liver membranes of TCDD-resistant and TCDD-sensitive rats after a single dose of TCDD.

Epidermal growth factor (EGF) receptor has been implied as having a role in certain actions of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). After a single dose of TCDD, the receptor has been shown to be downregulated in several tissues including the liver. Two rat substrains, the Han/Wistar (Kuopio; H/W) rat and the Long-Evans (Turku AB; L-E) rat exhibit over a 1000-fold difference in their sensitivity to the lethal effect of TCDD. This large sensitivity difference was utilized in the current study to investigate whether or not a correlation exists between TCDD lethality and biochemical endpoints related to the hepatic EGF receptor. In the TCDD-sensitive L-E strain both the B(max) of the EGF receptor and the receptor protein as measured by Western blots, decreased dose and time dependently. Ten days after a lethal dose of TCDD (50 µg/kg), the downregulation was 80%. In the resistant H/W strain, two non-lethal doses were used (50 and 500 µg/kg), since the lethal dose is not known. These doses caused a downregulation already at 4 days after dosing, but no further decrease by day 10. The activity of phosphoenolpyruvate carboxykinase (PEPCK, the main gluconeogenetic enzyme in the liver and a proposed target of TCDD) decreased in H/W rats at least to the same extent as in L-E rats at both 4 and 10 days. It is concluded that EGF receptor downregulation is different in the two rat strains studied, despite the fact that a classical Ah receptor-regulated response (CYP1A1 induction) is similar. The results demonstrate that downregulation of the EGF receptor by TCDD is strain-dependent as well as dose- and time-dependent.

Persistent organic pollutant levels in semi-domesticated reindeer (Rangifer tarandus tarandus L.), feed, lichen, blood, milk, placenta, foetus and calf.

A study concerning persistent organic pollutants in Finnish semi-domesticated reindeer was conducted in northern Finland. The aim of this study was to explore POP presence in different tissues of reindeer. In addition, it was studied how POPs are transported from food concentrates and lichen to reindeer hind tissues and further to the placenta, foetus, milk and calf. Concentrations of 17 polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/Fs), 37 polychlorinated biphenyls (PCBs) (including 12 dioxin-like PCBs), and 15 polybrominated diphenyl ethers (PBDEs) were analysed. In most of the reindeer muscle tissue samples PCBs were clearly dominating compounds (on average 58% of the total WHO-TEQ). The total WHO-TEQ was higher in the muscle tissue of reindeer calves than in their corresponding hinds (on average 1.7 pg/g fat vs. 1.1 pg/g fat, respectively). The total WHO-TEQ concentrations were higher in the muscle and liver tissues of reindeer hinds than in their blood or placentas. The foetuses had clearly lower WHO-TEQ concentrations than their corresponding hinds. The contribution of WHO-PCDD/F-TEQ to the total WHO-TEQ was somewhat higher in the liver than in the muscle tissue. The reindeer hind-calf pair, which had gone through the lichen diet, had on average higher WHO-PCDD/F- and PCB-TEQ concentrations in their tissues than the hind-calf-pair that had gone through the reindeer food concentrate diet. WHO-PCB-TEQs in the reindeer foetuses were equal with the concentrations of placentas. The reindeer foetuses contained generally more PBDEs than their corresponding hinds and placentas. This may indicate effective transport of these compounds through the placenta of reindeer.