35 research outputs found
Recommended from our members
The gut microbiota: a major player in the toxicity of environmental pollutants?
Exposure to environmental chemicals has been linked to various health disorders, including obesity, type 2 diabetes, cancer and dysregulation of the immune and reproductive systems, whereas the gastrointestinal microbiota critically contributes to a variety of host metabolic and immune functions. We aimed to evaluate the bidirectional relationship between gut bacteria and environmental pollutants and to assess the toxicological relevance of the bacteria–xenobiotic interplay for the host. We examined studies using isolated bacteria, faecal or caecal suspensions—germ-free or antibiotic-treated animals—as well as animals reassociated with a microbiota exposed to environmental chemicals. The literature indicates that gut microbes have an extensive capacity to metabolise environmental chemicals that can be classified in five core enzymatic families (azoreductases, nitroreductases, β-glucuronidases, sulfatases and β-lyases) unequivocally involved in the metabolism of >30 environmental contaminants. There is clear evidence that bacteria-dependent metabolism of pollutants modulates the toxicity for the host. Conversely, environmental contaminants from various chemical families have been shown to alter the composition and/or the metabolic activity of the gastrointestinal bacteria, which may be an important factor contributing to shape an individual’s microbiotype. The physiological consequences of these alterations have not been studied in details but pollutant-induced alterations of the gut bacteria are likely to contribute to their toxicity. In conclusion, there is a body of evidence suggesting that gut microbiota are a major, yet underestimated element that must be considered to fully evaluate the toxicity of environmental contaminants
4-(4-nitrobenzyl)pyridine tests for alkylating agents following chemical oxidative activation
A chemical activation system (CAS) designed to mimic the mammalian mixed-function oxidase enzymes was found to activate target compounds to reactive electrophiles. Activated compounds were assayed by reaction with 4-(4-nitrobenzyl)pyridine (NBP). A model nucleophile of 7-alkylguanine of nucleic acids, NBP produces a violet color following alkylation. Twenty compounds from several chemical classes were tested. The test generally gave positive and negative responses where expected. Two compounds, trichloroethylene and diethylnitrosamine, exhibited a linear Beer's law relationship in the concentration range tested. A high degree of linear correlation (r>0.97) was obtained for these compounds. Other compounds showed varying degrees of linear correlation from high correlation (r=0.94) to weak correlation (r=0.44). The CAS-NBP assay results were compared to bacterial mutagenicity and animal carcinogenicity test results when information was available. A good correlation (r=0.80) existed between direct alkylating activity and direct mutagenicity. Similar correlations existed between NBP alkylation following activation and mutagenicity following microsomal activation (r=0.73). Also, different correlations were observed between carcinogenicity and NBP alkylation following activation (r=0.69) and without activation (r=0.38).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/48076/1/244_2004_Article_BF00213289.pd
Perfluorooctane Sulfonate Plasma Half-Life Determination and Long-Term Tissue Distribution in Beef Cattle (Bos taurus)
Perfluorooctane
sulfonate (PFOS) is used in consumer products as
a surfactant and is found in industrial and consumer waste, which
ends up in wastewater treatment plants (WWTPs). PFOS does not breakdown
during WWTP processes and accumulates in the biosolids. Common practices
include application of biosolids to pastures and croplands used for
feed, and as a result, animals such as beef cattle are exposed to
PFOS. To determine plasma and tissue depletion kinetics in cattle,
2 steers and 4 heifers were dosed with PFOS at 0.098 mg/kg body weight
and 9.1 mg/kg, respectively. Plasma depletion half-lives for steers
and heifers were 120 ± 4.1 and 106 ± 23.1 days, respectively.
Specific tissue depletion half-lives ranged from 36 to 385 days for
intraperitoneal fat, back fat, muscle, liver, bone, and kidney. These
data indicate that PFOS in beef cattle has a sufficiently long depletion
half-life to permit accumulation in edible tissues
Distribution and Excretion of Perfluorooctane Sulfonate (PFOS) in Beef Cattle (<i>Bos taurus</i>)
Perfluorooctane
sulfonate (PFOS), a perfluoroalkyl surfactant used in many industrial
products, is present in industrial wastes and in wastewater treatment
plant biosolids. Biosolids are commonly applied to pastures and crops
used for animal feed; consequently, PFOS may accumulate in the edible
tissues of grazing animals or in animals exposed to contaminated feeds.
There are no data on the absorption, distribution, and excretion of
PFOS in beef cattle, so a 28-day study was conducted to determine
these parameters for PFOS in three Lowline Angus steers given a single
oral dose of PFOS at approximately 8 mg/kg body weight. PFOS concentrations
were determined by liquid chromatography–tandem mass spectrometry
in multiple tissue compartments. The major route of excretion was
in the feces (11 ± 1.3% of the dose, mean ± standard deviation)
with minimal PFOS elimination in urine (0.5 ± 0.07% of the dose).
At day 28 the mean plasma concentration remained elevated at 52.6
± 3.4 μg/mL, and it was estimated that 35.8 ± 4.3%
of the dose was present in the plasma. Plasma half-lives could not
be calculated due to multiple peaks caused by apparent redistributions
from other tissues. These data indicate that after an acute exposure
PFOS persists and accumulates in edible tissues. The largest PFOS
body burdens were in the blood (∼36%), carcass remainder (5.7
± 1.6%), and the muscle (4.3 ± 0.6%). It was concluded that
PFOS would accumulate in edible tissues of beef, which could be a
source of exposure for humans
Absorption and Excretion of <sup>14</sup>C-Perfluorooctanoic Acid (PFOA) in Angus Cattle (Bos taurus)
Perfluoroalkyl substances (PFASs), such as perfluorooctanoic
acid
(PFOA), are environmentally persistent industrial chemicals often
found in biosolids. Application of these biosolids to pastures raises
concern about the accumulation of PFOA in the edible tissues of food
animals. Because data on the absorption, distribution, metabolism,
and excretion (ADME) of PFOA in cattle were unavailable, a study was
conducted to determine pharmacokinetic parameters following a single
oral exposure (1 mg/kg body weight of <sup>14</sup>C-PFOA) in four
Lowline Angus steers. Radiocarbon was quantified in blood, urine,
and feces for 28 days and in tissues at the time of slaughter (28
days) by liquid scintillation counting (LSC) or by combustion analysis
with LSC with confirmation by liquid chromatography–tandem
mass spectrometry (LC-MS/MS). <sup>14</sup>C-PFOA was completely absorbed
and excreted (100.7 ± 3.3% recovery) in the urine within 9 days
of dosing. The plasma elimination half-life was 19.2 ± 3.3 h.
No <sup>14</sup>C-PFOA-derived radioactivity was detected in edible
tissues. Although PFOA was rapidly absorbed, it was also rapidly excreted
by steers and did not persist in edible tissues, suggesting meat from
cattle exposed to an acute dose of PFOA is unlikely to be a major
source of exposure to humans