Subacute exposure to lead promotes disruption in the thyroid gland function in male and female rats (original) (raw)
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Lead exposure causes thyroid abnormalities in diabetic rats
International journal of clinical and experimental medicine, 2015
Lead is a widely-spread environmental pollutant and a commonly-used industrial chemical that can cause multisystemic adverse health effects. However, the effects of lead exposure on diabetic animals have not been reported so far. The aim of this study is to evaluate the effects of lead exposure on thyroid, renal and oxidative stress markers in diabetic Wistar rats. Diabetes was induced with an intraperitoneal (i.p.) injection of streptozocin (STZ). Six weeks later, rats were exposed i.p. to either distilled water (control group) or 25, 50 and 100 mg/kg of lead acetate (treatment groups). We found a positive relationship between the administered doses of lead acetate and its measured levels in blood samples (P < 0.01). Treatment of diabetic animals with lead acetate resulted in significant weight loss (P < 0.001). It also caused an increase in thyroid stimulating hormone levels (P < 0.05) and reductions in thyroxine (P < 0.05) and triiodothyronine levels (P < 0.01), a ...
The effect of long-term low-dose lead exposure on thyroid function in adolescents
Environmental Research, 2006
This study investigated blood lead (Pb-B) levels and Pb-B effects on thyroid functions in long-term low-level-lead-exposed male adolescents who work as auto repairers. Pb-B and ALAD index (logarithm of activated d-aminolaevulinic acid dehydratase/nonactivated d-aminolaevulinic acid dehydratase) were measured as indicators of exposure to lead. Thyroid function tests including free thyroxine (FT4), free triiodothyronine (FT3), and thyrotrophin (TSH) were conducted and thyroid ultrasounds were performed in 42 lead-exposed adolescents and 55 healthy control subjects. Mean Pb-B levels and ALAD index were found significantly higher in the study group than in the normal control group (7.372.92 mg/dl vs. 2.0871.24 mg/dl, Po0:001 and 0.4470.26 vs. 0.2970.23, Po0:05, respectively). FT4 levels were found significantly lower in the study group (1.0270.18 mI/mL and 1.1270.14 mIU/mL, Po0:05). No subject in the control group had an abnormal FT4 level, but FT4 levels were found under normal limits in 11 subjects (26%) in the study group. FT3 and TSH levels in the study and control groups did not differ (P40:05). Thyroid volumes in the study and control groups did not exhibit any significant differences (P40:05). Pb-B was found to be negatively correlated to FT4 levels (r ¼ À0:20, P ¼ 0:044). This study revealed that long-term low-level lead exposure may lead to reduced FT4 level without significant changes in TSH and T3 levels in adolescents even at low Pb-B levels. r
Impact of lead exposure on pituitary-thyroid axis in humans
Biometals, 2000
Thyroid function tests (serum levels of thyroxine-T4, triiodothyronine-T3 and thyroid stimulating hormone-TSH) were performed in fifty-eight men (mean age: 31.7±10.6 years; mean duration of lead exposure: 156.9±122.7 months). These subjects were exposed to lead either as petrol pump workers or automobile mechanics. The mean whole blood lead (Pb-B) levels were 2.49±0.45 μmole/l (51.90±9.40 μg/dl) in the lead exposed workers and were approximately 5 times higher than in the control (n=35) subjects. No significant alteration was seen in their mean T3 and T4 levels as compared with the controls. Interestingly, T3 was significantly lower with the longer (210 months) exposure time in comparison with the group having shorter (29 months) exposure duration. The mean TSH levels were significantly (p<0.01) higher in workers exposed in comparison with the control group. This rise in TSH was independent of exposure time, but it was definitely associated with the Pb-B levels. The increase being more pronounced with mean Pb-B levels of 2.66±0.2 μ mole/l (55.4±4.25 μg/dl) when compared with the group having mean levels of 1.51±0.30 μmole/l (31.5±6.20 μg/dl). The rise is TSH associated with Pb-B levels was only statistical valid, however, the levels fall within the normal laboratory range. We thus conclude that the Pb-B levels of ≥2.4 μmole/l (50 μg/dl) could enhance the pituitary release of TSH without having any significant alterations in the circulating levels of T3 and T4.
Effects of lead on thyroid functions in lead-exposed workers
Central European Journal of Medicine, 2010
Lead exposure is a common public health problem. Exposure to the metal can cause hematological, gastrointestinal, rheumatological, endocrine, neurological and renal problems in humans. However, effects on the thyroid gland are controversial. We retrospectively investigated thyroid function parameters in 65 adult males who had been occupationally exposed to lead. We then compared the findings with those of 60 male patients who had no history of lead exposure or thyroid abnormalities, who served as the control group. The mean ages of the lead-exposed workers and the controls were 34.3 ± 7.9 and 32.9 ± 6.6 years respectively. Blood lead levels in the lead-exposed workers were significantly higher than in the control group. The lead-exposed workers were assigned to one of three groups according to their blood lead levels, as follows: 40–59 μg/dl, 60–79 μg/dl, or 80 μg/dl and above. Thyroid Stimulating Hormone (TSH) levels in the 80 μg/dl and above group were significantly higher than in...
Effect of inorganic lead on thyroid function of exposed workers
The effects of long-term exposure to lead on thyroid hormones are not clear. Unlike others, some studies report deleterious effects of inorganic lead on thyroid function. Methods: the potential endocrine disruption was evaluated in 141 lead-exposed workers and 141 controls free from any exposure to this toxic. In the exposed group, the exposure-retained factors are blood lead level (BLL), which reflects recent exposure, the cumulative blood lead, which reflects the old exposure (from hiring) and zinc protoporphyrin (ZPP), a marker of the intermediate exposure. Regarding the control group, only blood lead was measured. Results: If TSH and FT4 were significantly higher in the exposed group, however FT3 was significantly higher in the non-exposed group. In the exposed group, FT3 is inversely correlated with age, FT4 is positively correlated with BLL and ZPP, and TSH is positively correlated with ZPP. Conclusions: the results suggest the existence of a deleterious effect of inorganic lead on thyroid function. Furthermore, it appears that only the intermediate exposure seems to be responsible for this action.
Effect of lead on thyroid function in sheep
Iranian Journal of Veterinary Research, 2009
Department of Clinical Sciences, School of Veterinary Medicine, Shiraz University, Shiraz, Iran; Graduated from School of Veterinary Medicine, Shiraz University, Shiraz, Iran and Department of Veterinary Medicine, School of Agriculture, Rasht Branch, Islamic Azad University, Rasht, Iran; Ph.D. Student in Large Animal Internal Medicine, Department of Clinical Sciences, School of Veterinary Medicine, Shiraz University, Shiraz, Iran
Age-related effects of lead poisoning on sex hormones in adult male Wistar rats, 2016
The World Health Organization (WHO) estimates that, about a quarter of the diseases facing mankind today occur due to prolonged exposure to environmental pollution, and that most of these environment-related diseases are however, not easily detected and may be acquired during childhood and manifested later in adulthood. The aim of this work was to determine the sub-chronic effects of lead poisoning on and some sex hormones, as well as age-related changes on Wistar Rats. Thirty (30) of 3-, 5-, and 7-months old age-groups male Wistar rats were selected; each age group was divided into experimental (lead fed) and control (distil water fed) groups. The levels of sex hormones (LH, FSH and Testestrone) were measured using ELISA method, while blood lead concentration was determined using the method of Atomic Absorption Spectrophotometer. There was a significant (P<0.05) increase between experimental and control groups in blood lead concentration and insignificant (P˃0.05) increase in LH in both experimental and control groups. Significant (P<0.05) decrease in body weight, testosterone levels, FSH was observed between experimental and control groups. The effect of lead (Pb) on testosterone levels was more pronounced in older animals. It was concluded that, ingestion of lead acetate has an age related effect on male sex hormones in older rats.
Impact of lead toxicity on male rat reproduction at hormonal and histopathological levels
Toxicological & Environmental …, 2010
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Toxicology and Applied Pharmacology, 1996
The reproductive toxicity and growth effects of developmental lead exposure were assessed using a rat model in which 0.6% (w/v) lead acetate was administered in the drinking water ad libitum. Three series of experiments were conducted in which lead exposure was initiated beginning in utero, prepubertally, or postpubertally. Lead effects were measured on reproductive physiology and endocrinology, sexually dimorphic hepatic testosterone hydroxylation, and growth rates in both male and female animals. In male animals secondary sex organ weights were significantly decreased only in animals exposed prepubertally. In addition, serum testosterone levels were significantly suppressed, most severely in animals exposed from in utero (in the in utero group). Little effect was observed in adult female rats. However, in female animals exposed prepubertally, delayed vaginal opening and disrupted estrus cycling was observed. More severe reproductive disruption was accompanied by suppression of circulating estradiol in the in utero group. Effects on circulating sex steroids were accompanied by variable effects on circulating luteinizing hormone (LH) levels, pituitary LH, and pituitary LH beta mRNA, suggesting a dual site of lead action: (a) at the level of the hypothalamic pituitary unit, and (b) directly at the level of gonadal steroid biosynthesis. Prepubertal growth in both sexes was suppressed 25% in the in utero group. However, pubertal growth rates were significantly suppressed only in male animals and postpubertal growth was not significantly different from controls in any of the experiments, despite continued exposure to high lead levels in the drinking water. In addition, at age 85 days, male-specific hepatic hydroxylation of testosterone at positions 2 alpha and 16 alpha, which is catalyzed by a cytochrome P450 isozyme CYP 2C11, itself regulated by sexually dimorphic growth hormone secretion, was unaffected. This suggests that the growth effects of lead are possibly due to a delay in the development of sex-specific pituitary growth hormone secretion patterns rather than a persistent developmental defect. Thus, the reproductive and growth effects of lead are complex and sex-dependent, and appear to involve multiple sites on the hypothalamic-pituitary-gonadal axis.
From Molecular to Functional Effects of Different Environmental Lead Exposure Paradigms
Biology
Lead is a heavy metal whose widespread use has resulted in environmental contamination and significant health problems, particularly if the exposure occurs during developmental stages. It is a cumulative toxicant that affects multiple systems of the body, including the cardiovascular and nervous systems. Chronic lead exposure has been defined as a cause of behavioral changes, inflammation, hypertension, and autonomic dysfunction. However, different environmental lead exposure paradigms can occur, and the different effects of these have not been described in a broad comparative study. In the present study, rats of both sexes were exposed to water containing lead acetate (0.2% w/v), from the fetal period until adulthood. Developmental Pb-exposed (DevPb) pups were exposed to lead until 12 weeks of age (n = 13); intermittent Pb exposure (IntPb) pups drank leaded water until 12 weeks of age, tap water until 20 weeks, and leaded water for a second time from 20 to 28 weeks of age (n = 14);...