Bioavailability and metabolism of hexavalent chromium compounds †

Intratracheal instillation of ⁵¹CrCl₃ in anaesthetized rabbits resulted in partial absorption. In blood, the absorbed material was entirely confined to the plasma compartment. Only trace amounts were deposited in liver and kidney. By contrast, after similar application of Na, ⁵¹CrO₄ the bulk of blood radioactivity was present in red blood cells (RBC). Substantial deposition occurred in liver and kidneys. It is concluded that Cr(VI) may enter the body unreduced via the lung and is partially deposited in cells over a prolonged period of time.

Since chromium was accumulated in liver after administration of Cr(VI) we investigated the intracellular disposition of Cr(VI) in the isolated perfused liver. No significant sex differences in chromium distribution were observed. At the end of the experiments (1 h), 60% of the applied dose (312μg Cr/liver) was located in the cytosol, whilst 14% was in the mitochondria, 9% in the microsomal pellet and 2% was associated with the nuclei. Gel chromatography of the cytosolic compartment showed that the overwhelming part of chromium was eluted in fractions with an apparent molecular weight of 6,000 dalton. These fractions exhibited absorption maxima at 410nm and 548nm. It is concluded, that cytosolic reduction might be the main intracellular redox pathway for chromates. This view was confirmed by monitoring the reaction of Cr(VI) with GSH in vitro. GSH reduced Cr(VI) without further cofactors under formation of GSH‐chromium complexes, which possibly represent major intermediates in the metabolism of Cr(VI).     

Transfer of the insecticide [<Superscript>14</Superscript>C] imidacloprid from soil to tomato plants

The fate of imidacloprid was investigated in tomato plants during 75 days in soil contaminated by ¹⁴C-imidacloprid. Leaves and fruits were separately analysed for total radioactivity and metabolites. Almost 85% of plant radioactivity was translocated to shoots. Radioactivity concentrations decreased from bottom leaves to top leaves. Desnitro-imidacloprid was the main metabolite in leaves. Nevertheless, more than 50% of the leave radioactivity corresponded to imidacloprid. Residue concentrations were similar in all fruits (62.9 ng g⁻¹), irrespective of their position on plant. In fruits more than 85% of the radioactivity was due to imidacloprid. The small fraction of residues translocated to fruits depended on the low xylem flow in fruits.     

Nickel toxicity in partially hepatectomized rats: I. accumulation of radioactive nickel in various organs and subcellular fractions of liver

The distribution of radioactive nickel (50 μmol/kg/200μ Ci S.C.) was studied in various organs as well as in the hepatic subcellular fractions of sham operated and partially hepatectomized rats at 16 hr after injection. ⁶³Ni was maximally accumulated in kidney followed by lung, liver, heart and spleen. The incorporation of ⁶³Ni was lowered in partially hepatectomized rats compared to sham operated ones. Subcellular binding of ⁶³Ni showed significantly high affinity of nickel to cytosol followed by nuclear, mitochondria and microsomes in both the groups.     

Reproduction of the estuarine mysid Taphromysis bowmani (Crustacea: Malacostraca) in fresh water

We have monitored the incorporation of ³H-glycine into, and the excretion of, soluble tissue and extrapallial fluid proteins in the hardshell clam Mercenaria mercenaria in an attempt to follow some of the metabolic events that occur antecedent to shell deposition. After incubating at 20°C for 48 h, clams were killed and the distribution of incorporated and unincorporated tritium in seawater, mantle fluid, hemocoelic-tissue fluid, extrapallial fluid and tissue was determined. Most of the incorporated tritium was in the insoluble tissue proteins. Much more incorporated tritium was found in the hemocoelic-tissue fluid fraction than in the extrapallial fluid. We assume that most of the radioactivity we followed was due to free or incorporated radioactive glycine. The ratio of ³H-protein to ³H-glycine was greater in the extrapallial fluid than in the hemocoelic-tissue fluid, suggesting either protein secretion into or glycine removal from the extrapallium. We also observed that both ³H-protein and ³H-glycine concentrations were higher in the mantle fluid than in the external sea water, although the ratios of ³H-glycine to ³H-protein in these two fluids were not different.     

Identification of protein biomarkers of mercury toxicity in fish

Bioaccumulative metals such as mercury are found in increasing amounts in fish and their consumers. In the region of the Madeira River, in the Brazilian Amazon, mercury (Hg) is a predominant contaminant in the aquatic ecosystem. There is therefore a need to find specific biomarkers of mercury toxicity in fish to monitor contaminations. Here, mercury-bound proteins were identified in the liver tissues of fishes Mylossoma duriventre and Brachyplatystoma rousseauxii. Mercury was quantified in liver tissue, pellets and protein spots by graphite furnace atomic absorption. Proteins were fractionated by two-dimensional polyacrylamide gel electrophoresis and identified by mass spectrometry with electrospray ionization. We identified nine proteins linked to mercury and that presented biomarker characteristics of mercury. Among the proteins identified, isoforms of parvalbumin, ubiquitin-40S ribosomal protein S27a, brain-specific angiogenesis inhibitor 1-associated protein 2-like protein 2 and betaine–homocysteine S-methyltransferase 1 are notable for having the molecular function of binding to metallic ions.     

The essential amino-acid requirements of the prawnPalaemon serratus. The growth of prawns on diets containing proteins of different amino-acid compositions

Two specimens ofPalaemon serratus Pennant (of about 4 g wet weight) were each given intrahaemocoelic injections of [U-¹⁴C] acetate. They were maintained under controlled conditions, and the release of¹⁴CO₂ and other labelled metabolites was followed for 6 days. The prawns were then sacrificed and fractionated into trichloroacetic acid soluble compounds, lipids, nucleic acids and a protein/chitin residue. Little or no¹⁴C had been incorporated into arginine, methionine, valine, threonine, isoleucine, leucine, lysine, histidine, phenylalanine and tryptophan. It was inferred thatP. serratus cannot synthesize these amino acids from ordinarily available materials, and that the prawns have an absolute dietary requirement for them. The glucosamine isolated from the protein/chitin residue contained more radioactivity than any of the other compounds examined. This implies a rapid turnover of glucosamine and chitin inP. serratus. The gain in weight of prawns fed on compound diets containing freeze-dried cod muscle was about 70% that of prawns fed on fresh mussel mantle. Predigestion of freeze-dried cod muscle with proteolytic enzymes did not significantly enhance its nutritional valve as assessed by increases in weight. Prawns fed two other compounded diets containing proteins of low nutritional value (gelatin and zein, respectively) grew at about 1/5 the rate of prawns fed fresh mussel mantle. Supplementation of the gelatin and zein in these diets with tryptophan, and with lysine plus tryptophan, respectively, failed to augment their nutritional value significantly.     

Characterization of the liver cytochrome P450 in the marine fish Mugil cephalus and effects of some hydrocarbons on the mixed-function oxidase components

The marine fish Mugil cephalus was caught in the Bay of Marseilles (France) in 1985 and the liver microsomal cytochrome P₄₅₀ was identified at a concentration of about 0.230 nmol mg^-1 protein. Optimal assay conditions were established to measure two mixed-function cytochrome P₄₅₀-dependent oxidases: aniline hydroxylase and p-nitroanisole O-demethylase. Induction of cytochrome P₄₅₀ occurred after exposure of mullet to an aromatic hydrocarbon and a water-soluble petroleum fraction. The liver cytochrome P₄₅₀ was solubilized and purified. The monomer molecular weight of partially purified cytochrome P₄₅₀, determined by sodium dodecyl-sulfate-gel electrophoresis, was 51 000.     

Intracellular localization and binding of technetium-95m in the seastar Marthasterias glacialis

The subcellular distribution of technetium was studied using the seastar Marthasterias glacialis which had previously ingested prey labelled with ^95mTc either as pertechnetate (VII) or in the reduced state (IV). The majority of the Tc [98% (IV) and 96% (VII)] was taken up and retained in the pyloric caeca, the gland responsible for digestive and food storage processes. Differential centrifugation and separation techniques have demonstrated that, at the subcellular level, technetium in the pyloric caeca was largely associated with the lysosomes. ^95mTc (IV) was distributed between the lysosomes and the soluble fraction to roughly the same degree, whereas pertechnetate was more strongly associated with the lysosomal fraction. Chromatography of the cytosol by gel filtration indicated the presence of two distinct protein compounds which were responsible for binding virtually all of the technetium in the soluble fraction. Technetium had a greater relative affinity for the low molecular weight compound, more so for Tc (VII) than for Tc (IV). This anionic protein had an apparent molecular weight of approximately 10 000, and thus may play a role in metal detoxification mechanisms at the cellular level.     

Isolation of heavy metal binding proteins from marine vertebrates

Cadmium binding proteins have been isolated from liver homogenates of marine vertebrates by ultracentri fugation and gel filtration. Liver samples of the Atlantic grey seal Halichoerus grypus and the Pacific fur seal Callorhinus ursinus contain measurable quantities of cadmium binding protein. The copper rock fish Sebastodes caurinus showed an increase in hepatic cadmium binding protein on administration of CdCl₂, in agreement with the known inducible nature of the protein isolated from terrestrial animals. The apparent molecular weights of the isolated proteins were 9000 for the grey seal, 10,000 for the fur seal, and 11,000 for the copper rock fish, as determined by gel filtration.     

Toxicokinetics,metabolism, and microsomal studies of chlorpropham in rats

A study on the toxicokinetic behavior, metabolism of chlorpropham, and its effect on cytochrome P₄₅₀ from liver microsomes was carried out in albino rats after a single and consecutive oral administration at 500?mg?kg^?1 body weight for 10 and 20 days. Chlorpropham was detected in the blood at 0.08?h (11.43?±?1.72?µg?mL^?1) reaching a maximum concentration at 2?h (30.90?±?2.55?µg?mL^?1) and a minimum at 48?h (1.95?±?0.20?µg?mL^?1) after a single oral administration of 500?mg?kg^?1. The absorption rate constant (K _a) was 0.66?±?0.48?h^?1. The Vd _area (18.01?±?2.78?L?kg^?1) and t _1/2 β (12.23?±?1.96?h) values suggested a wide distribution and long persistence of the compound in the body, respectively. The higher Cl_R (0.82?±?0.00?L?kg^?1?h^?1) compared to Cl_H (0.18?±?0.02?L?kg^?1?h^?1) value indicated that a major portion of chlorpropham was excreted through the urine (30%) compared to the faeces (2.81%). Chlorpropham residue was detected in all tissues of rat at 0.25?h while its metabolite, meta-chloroaniline was detected in liver, kidney, heart, lung, and spleen tissue at 0.25?h. Meta-chloroaniline was not detected in skeletal muscle, brain, fat, and stomach tissue at any time of the observation period. Maximum concentrations of chlorpropham and meta-chloroaniline were detected at 2?h (except in the spleen), and minimum concentrations of chlorpropham at 24 (heart, lung, spleen, skeletal muscle, and stomach) and 48?h (liver, kidney, brain, and fat tissue) respectively; and meta-chloroaniline at 24?h (except heart and spleen). The tissue half-life of chlorpropham in rat varied from 3.80 to 11.60?h. Repeated oral administration of chlorpropham at 500?mg?kg^?1 for 10 and 20 days caused an induction of the liver microsomal pellet of rat.     

口服纳米银对大鼠的生物有效性及其体内分布的研究

由于独特的抗菌特性，纳米银(AgNP)在诸多领域得到广泛应用，但是其生物有效性、动物组织分布及排出尚不清楚。将聚乙烯吡咯烷酮包被的AgNP溶液按照10 mg kg^-1给雌性SD大鼠灌胃，采用ICP-MS检测SD大鼠组织、粪便及尿液中总银浓度。实验结果表明，AgNP通过小肠吸收后，可以通过血液循环快速分布在肝、肾、脾、肺、脑等靶器官。灌胃后1 h，大鼠各组织中总银浓度达到最大值(肝、肾、脾、肺、脑中银浓度分别为0.29 ± 0.13 mg kg^-1、0.23 ± 0.04 mg kg^-1、0.17 ± 0.05 mg kg^-1、0.11 ± 0.01 mg kg^-1、0.06 ±0.02 mg kg^-1)，之后银浓度随时间降低直至和对照组无显著性差异。在灌胃途径下，AgNP对SD大鼠的有效性为8.5%，且73%的AgNP是通过粪便的途径排出体外。     

Phytochemical screening and toxicological profile of methanolic extract of Picralima nitida fruit-rind (Apocynaceae)

The methanol (M) extract of the fruit-rinds of Picralima nitida (PN) was analyzed phytochemically and evaluated for its toxicity effect in Wistar rats. The rats were administered graded doses (0.75, 1.5, 3, and 6 g kg^?1 p.o) of the extract daily for 6 weeks and the toxicological effect of these varying levels of extract were examined on the serum, hepatic, and renal concentration of biochemical parameters as well as the histopathology of tissue section of these liver, kidney, and lungs. Clinical signs and hematology were also evaluated. Phytochemical analysis revealed that alkaloids and polyphenols were major compounds. Both biochemical and histopathological data presented demonstrate dose-dependent signs of toxicity. Our results show a significant elevation in serum concentration of aspartate amino-transferase, alanine amino-transferase, glucose, creatinine, total cholesterol, and protein with high-dose of PN treatment tested. PN also caused a significant reduction in hepatic malondialdehyde and a slight increase in glutathione concentration at the lowest dose tested. Renal urea level was reduced significantly in test groups. A significant change was observed in the relative weights of the spleen, heart, and kidneys. The total white blood cell count was reduced, whereas the hematocrit level was increased remarkably in animals that received high doses of the extract. The acute toxicity LD₅₀ was estimated at 14.5 and 12.5 g kg^?1 body weight for male and female, respectively. These results show that prolonged usage of this extract at 1.5–6 g kg^?1 dose could cause liver, kidney, and lung injury, while the effect was mild at small dose levels (0.75 g kg^?1). Thus, the extract should be taken with caution bearing in mind that higher doses could affect the liver, kidneys, and lungs.     

Isolation of novel metal-binding proteins distinct from metallothionein from spotted seatrout (Cynoscion nebulosus) and Atlantic croaker (Micropogonias undulatus) ovaries

Metal-binding proteins were isolated from ovaries of the spotted seatroutCynoscion nebulosus and the Atlantic croakerMicropogonias undulatus collected in 1988 near Port Aransas, Texas, USA. Gel-filtration analysis of spotted seatrout trout ovarian cytosolic fraction on Sephadex G-75 revealed the presence of three zincbinding protein fractions. A major zinc/calcium-binding protein fraction had a low molecular weight (M _r)(6 000 to 10 000), similar to mammalian hepatic metallothionein (MT). All the metals were displaced from this fraction following saturation with exogenous cadmium. After exposure of Atlantic croaker to 2 mg cadmium l^–1 seawater for 2 mo, the majority of the cadmium in the ovarian cytosolic fraction was associated with a similar low molecular weight protein fraction. These proteins were further purified by heat treatment and sequential acetone precipitation. Three isoforms were isolated by reversephase high-performance liquid chromatography. All the isoforms were found to be distinct from mammalian MT, based on amino acid composition. The major isoform contained low amounts of cysteine (approximately 5 residues per molecule) and aromatic amino acids, compared to high amounts of cysteine (typically 17 to 20 residues/molecule) and a lack of aromatic amino acids for mammalian MT. All the ovarian protein isoforms contained more glutamate than mammalian MT. The spotted seatrout and Atlantic croaker ovarian isoforms showed a high degree of homology with metal-binding proteins isolated from mammalian gonadal tissues. The results suggest a physiological role for these metal-binding proteins in developing vertebrate ovaries as well as an involvement in the sequestration of cadmium following environmental exposure.     

Disposition of bisphenol A in pregnant mice and fetuses after a single and repeated oral administration

The risk assessment of bisphenol A (BPA) on the development of offspring of humans is an important issue. There have been some reports on the fate of BPA in rodents, but information on the BPA level in fetal organs essential for the extrapolation to humans is inadequate. In the present study, we investigated the distribution pattern of ¹⁴C-BPA-derived radioactivity in fetal tissues following administration of 10?mg/kg ¹⁴C-BPA to the pregnant mice. The radioactivity was rapidly transferred through placenta and distributed to all fetal organs including reproductive organs and brains in a similar level. The concentration declined slowly compared with dams. Analysis of metabolites in fetuses showed that a fraction of BPA was unexpectedly large compared to the maternal blood. There was no clear effect of the fetal position in a uterus to influence the radioactivity concentration in whole fetuses. The dose dependence of pharmacokinetics should be recognized to extrapolate the pharmacokinetic result from animal experiments at high doses to humans at low doses. Similar experiments were conducted with an addition of two doses, 1 and 100?mg/kg, respectively. The pharmacokinetics seemed to be linear between 1 and 10?mg/kg, although at 100?mg/kg BPA was absorbed slowly and the radioactivity concentrations in fetuses were much higher than expected based on the linear dose dependence. Repeated doses were administered to pregnant mice since humans are exposed to BPA chronically. Radioactivity level in most of the fetal tissues on repeated administration was higher than single administration.     

Combined effects of copper and cadmium on Chlorella pyrenoidosa H.Chick: subcellular accumulation,distribution, and growth inhibition

Disposal of waste into aquatic ecosystems may cause microalgae to be exposed to various metals, e.g. copper and cadmium. The effects caused by combinations of metals may be more serious. Evaluations of subcellular fate, bioaccumulation, and biological effects of metals on aquatic organisms are generally derived from experiments with individual metals. The present study aims to evaluate the effects of exposure of Chlorella pyrenoidosa to copper and cadmium in combination on subcellular accumulation, distribution, and growth. The algae were exposed for 72 h to copper at concentrations of 13 – 25 µmol L^?1, cadmium at about 6 µmol L^?1, and combinations thereof. The levels of copper and cadmium in subcellular organelles, heat-denaturated protein, metal-rich granules, and heat-stable protein were determined by atomic absorption spectrometry. Exposure of C. pyrenoidosa to copper and cadmium in combination inhibited growth more strongly than copper and cadmium individually. Highest accumulation was observed in metal-rich granules and heat-stable proteins. Administration of both metals in combination affected their subcellular distribution: copper was mainly distributed into the metal-rich granules (70%–80%) and heat-stable proteins (9%–24%), cadmium in the metal-rich granules (88%–98%).     

Effects of nonylphenol on ovarian cancer cells PEO4 c-myc and p53 mRNA and protein expression

The molecular mechanisms underlying proliferation and apoptosis induced by p-nonylphenol (NP) through regulation of mRNA and protein expression of c-myc, p53 mRNA and the protein was investigated using ovarian cancer PEO4 cells. PEO4 cells were grown in the Dulbecco's modified Eagle medium (DMEM), 3(4,5-dimethylthiazol-2-yl) 2,5-diphenyltetrazolium bromide (MTT) assay was employed to investigate cell proliferation. RT-PCR and immunohistochemistry was performed to determine mRNA and protein expression of PEO4 c-myc and p53. Within the range of approximately 8–9×10^?7 mol L^?1, NP stimulated proliferation in PEO4 cells in a concentration-and time-dependent manner. RT-PCR and immunohistochemistry analyses revealed that treatment with 32 × 10^?7 mol L^?1 NP for 72 hr resulted in increased mRNA and protein expression of PEO4 c-myc and p53. Evidence indicates that NP exerted estrogenic actions and stimulated proliferation in estrogen responsive ovarian cancer PEO4 cells by up-regulation of c-myc mRNA and protein expression.     

Histopathological alterations of Nile tilapia, Oreochromis niloticus in acute and subchronic alachlor exposure

Histopathological alterations in Nile tilapia, Oreochromis niloticus, aged 3 months and subjected to acute and subchronic alachlor exposure were studied by light microscopy LC50 values of alachlor for 24 hr 48 hr, 72 hr and 96 hr were 963.6, 563, 448, and 381.9 microg l(-1), respectively and the maximum acceptable toxicant concentration (MATC) was 350 microg l(-1). Fish were exposed to 381.9 (acute) and 35 microg l(-1) (sub-chronic) of alachlor for 24, 48, 72 and 96 hr and 90 days, respectively Gill lamellae and kidney tubules were the primary target organs for the acute toxic effect of alachlor while in the subchronic exposure, the toxic effect on the gills was less marked than that of the kidneys and liver Gill alterations included edema of the epithelial cell system, aneurisms with some ruptures, hypertrophy and hyperplasia of epithelial cells. The liver showed hydropic swelling of hepatocytes and vacuolation. Lipid vacuoles were observed in hepatocytes in the second and third month of subchronic exposure. The kidney showed hydropic swelling of tubular cells, lipid vacuole accumulation in many tubules, and nuclear pyknosis. The findings of this study could be used as a guideline forbiomonitoring programs on populations of Nile tilapia cultured near alachlor contaminated areas.     

Cadmium bioaccumulation in organs of the scallopMizuhopecten yessoensis

Cadmium and Zinc content was determined in organs of the Japanese scallopMizuhopecten yessoensis, collected in 1984 from the Sea of Japan and aged between 1 and 8 yr. Under conditions of background Cd, Cd concentration in hepatopancreas and kidney increased linearly with age from 39 to 400µg g^?1 dry wt in hepatopancreas, and from 100 to 640µg g^?1 dry wt in kidney. Such a pattern was not determined for Zn. Cd concentration in muscle, mantle and gill did not exceed 6µg g^?1 dry wt in the oldest scallops. In subcellular fractions of the hepatopancreas, cytosolic Cd accounted for 71.7% in 1-yr-old scallops and 98.8% in 8-yr-olds. A similar ratio was established for gills, although gill Cd content was an order of magnitude lower. Analysis of Cd distribution in cytoplasmic proteins (of different molecular weight) in the hepatopancreas, showed that the amount of Cd bound to metallothionein-like proteins increases with scallop growth. A considerable amount of Cd also was detected in high molecular weight proteins. Thus, Cd accumulation, with age, in organs of the Japanese scallop is due to metal binding by cytoplasmic proteins.     

Effect of salinity adaptation on nitrogen metabolism in the freshwater fish Tilapia mossambica. I. Tissue protein and amino acid levels

Water, proteins and total free amino acids were estimated in different tissues of the euryhaline fish Tilapia mossambica after adaptation to various strenghts of sea water. The water content did not vary significantly in any tissue on salinity adaptation. The soluble and insoluble proteins displayed a general and considerable decrease in muscle, liver and heart; the decrease in the soluble fraction in the heart and the proteins of the muscle in 75% sea water (100% sea water=32.5 S) were significant. The gill proteins did not alter with salinity; the kidney proteins tended to increase slightly in 100% sea water (SW). The total free amino-acid content decreased insignificantly in all tissues on adaptation to 25% SW; in higher salinities, however, the content increased significantly. This increase was sudden and steep in 50% SW, and gradual and less steep in 75 and 100% SW. It is suggested that constancy in water content may contribute to the great adaptability of T. mossambica to heterosmotic media, and that the total free amino acids may be involved in isosmotic intracellular regulation. The possibility of amino acid increase as a result of protein breakdown is also indicated.     

Pharmacokinetics of [14C]-atrazine in rhesus monkeys,single-dose intravenous and oral administration

This is the first study regarding the pharmacokinetics of [¹⁴C]-atrazine conducted with rhesus monkeys. The animals received one dose (0.25 mg) intravenously (IV) or three doses (1, 10, or 100 mg) orally. Plasma, urine, and feces were collected at defined times up to 7 days post-dosing. Sample radioactivity was measured to determine the mass equivalent. IV administered [¹⁴C]-atrazine disappeared rapidly from blood, with an elimination half-life of about 5.5 ± 1.1 h. The pharmacokinetic profiles of [¹⁴C]-atrazine following oral administration at the three dose levels show that kinetic parameters such as AUC and C _max are linearly correlated with the dose. Seven days after dosing, urinary and fecal excretion of [¹⁴C]-atrazine reached 99% of total administered dose in the IV group and 91–95% in the three oral dose groups. In the IV-administered monkeys, approximately 85% of the dose was excreted in urine and 12% in feces. In three oral dose groups, urinary and fecal radioactivity recoveries approximated 57% and 21%, 58% and 25%, and 53% and 35%, respectively. More than 50% of the total urinary excreted radioactivity was found within the first 24 h after dosing. In conclusion, the principal elimination of [¹⁴C]-atrazine, IV and orally administered, is via urine. The oral bioavailability was 60% or higher. There was a significant linear correlation between administered oral dose and plasma concentration. Overall oral dose accountability ranged from 91% to 95%. Data generated may be useful in the risk assessment of human exposure to environmental atrazine contamination.