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PubMed2003

Toxicity assessment of sediments containing tributyltin around Hong Kong harbour.

Rather high levels of tributyltin (TBT) in sediments were found in certain areas around the Hong Kong coastline. Sediments from two contaminated sites (Tsing Yi and Yam O) and two clean sites were used to study the release of TBT contaminants from resuspended sediment to the water column by elutriate tests. The chemical analysis data of elutriates were compared with the effective or lethal concentrations from the toxicity tests of spiked solution using marine microalga (Dunaliella tertiolecta) and benthic invertebrate (Melita koreana) to assess the potential ecotoxicological impacts arising from the dredging work. Concentrations of TBT in filtered sediment elutriates were mostly below 0.002 microg/l which suggested that very little of TBT was released in soluble form. The lethal toxicity of TBT for the invertebrate expressing as 10 day-LC(50) was 2.31 microg/l for TBT and the alga expressing as 48 h-EC(50) was 0.46 microg/l. The results of this evaluation demonstrated that the release of TBT from two contaminated sites during dredging was unlikely to attain the effective or lethal concentrations on the two test species.

Amphipoda↗
PubMed1996

Pre-implantation embryonic loss induced by tributyltin chloride in rats.

The effect of tributyltin chloride (TBTCl) administered during early pregnancy on pregnancy maintenance was evaluated in rats. Inseminated females were orally administered TBTCl at a dose of 0, 8.1, 12.2 or 16.3 mg/kg on day 0 through day 7 of pregnancy. Females were sacrificed on day 20 of pregnancy and pregnancy outcome was determined. Pregnancy failure, which was evidenced by absence of implantation sites, was found in 0 of the 10, in 2 of the 11, in 10 of the 14 and in 10 of the 13 females at 0, 8.1, 12.2 and 16.3 mg/kg, respectively. The rate of pregnancy failure was significantly higher in the 12.2 and 16.3 mg/kg groups than that in the control group. In females with successful pregnancy, the numbers of corpora lutea, implantations and post-implantation loss per litter were comparable across all groups. No increase in the incidence of malformed fetuses was found in any TBTCl-treated groups. Thus it appears that TBTCl causes pregnancy failure after administration during very early pregnancy.

Administration, Oral↗
PubMed1998

Risk assessment and immunotoxicology.

In general toxicity testing, maximal acceptable concentrations are derived from no-observed adverse effect levels (NOAEL) in rodents. Risk assessment then considers safety factors for the interspecies difference, and intraspecies variability. This approach can be used for assessing maximal acceptable concentrations for chemicals inducing direct immunotoxicity, resulting in e.g. reduced resistance to infections. As for predictive testing of chemicals in terms of sensitization, laboratory animal data are mostly used for risk assessment as well. Generally, the assessment of risk for chemicals that induce contact sensitivity is limited to hazard identification, and risk management is restricted to labeling. An alternative type of evaluation of the risk of adverse effects due to exposure to immunotoxic chemicals may be the so called parallellogram approach. In this parallellogram there are four cornerstones, one of which is the health effect of exposure to a chemical, assessed as an endpoint (e.g. infection model) in experimental animals, and another the quantitative prediction of this endpoint in humans. The other cornerstones are assays of parameters that are relevant to the mechanism of the adverse effect in experimental animals and humans, and are used for species comparison. Species comparisons between the animal species used for hazard identification and humans are crucial for extrapolation of animal data to the human situation. This approach can be used to provide relevant information on the dose-response relationship in humans. In concert with information on actual exposure, such data can then be used for the characterization of risk for adverse health effects in humans. Such approaches have been used for chemicals that exert direct immunotoxic activity (bis(tri-n-butyltin)oxide (TBTO)), and may hold promise for the risk evaluation of chemicals that exert skin sensitizing properties.

Animals↗
PubMed2000

Effects of tributyltin on the MFO system of the clam Ruditapes decussata: a laboratory and field approach.

The in vivo interaction of tributyltin (TBT) with the microsomal monooxygenase (MFO) system of the clam Ruditapes decussata was studied. For this purpose, two experiments were designed: (1) a laboratory exposure to increasing nominal doses of TBT (90, 454 and 2268 ng l(-1)) for 1 week and (2) a clam transplant from a clean area to an organotin polluted marina for periods of up to 5 weeks. Chemical analysis of organotins in clam tissue was used to relate TBT body burden to the MFO response. Neither the laboratory nor the field transplant experiment showed any significant TBT effect on the clam's digestive gland MFO components (cytochrome P450 and cytochrome b(5)). However, a significant elevation in the NADPH cytochrome (P450) reductases at the low and medium TBT doses in the laboratory and a significant decrease in NADH cytochrome (b(5)) reductases, 1 week after the field transplant, was observed with further recovery to control levels thereafter.

Animals↗
PubMed2003

Steroidogenesis during in vitro maturation of bovine cumulus oocyte complexes and possible effects of tri-butyltin on granulosa cells.

Steroids are known as important factors on the route of oocytes development and cumulus oocyte complexes (COC) as well as follicular granulosa cells (GC) are suggested to be themselves involved in steroidogenesis. The aim of this study was to characterize such a local sex steroidogenic system during in vitro maturation (IVM) of bovine COCs according to the production of estradiol (E), testosterone (T) and progesterone (P). The expression of two steroid-converting key-enzymes was measured in parallel by quantitative RT-PCR. Furthermore, possible effects of the environmental pollutant tri-butyltin (TBT) were elucidated for the first time on bovine COC and GC in vitro concerning that steroidogenic system. During IVM of bovine COCs concentrations of P increased continuously, corresponding with steady-state levels of 3-beta-hydroxy-steroid-dehydrogenase (HSD) transcripts. In contrast, E together with P450 aromatase mRNA (ARO) increased in the first hours of IVM but declining thereafter, whereas T reached almost balanced levels. However, TBT showed only slight effects during IVM of COC. In cultured GC, LH caused highest P- and E-production within 24h and treatment with 50pM TBT induced a significant decrease of E in contrast to 100pM TBT and the control. These results indicate, that (1) COCs were able to modulate their steroidogenic environment in vitro and that (2) TBT may possibly influence or disturb steroidogenesis in the cows reproductive tract shown here for GC.

Animals↗
PubMed1999

Regulation of intestinal peptidases by nutrients in human fetuses and children.

Nutrient interactions during intestinal digestion has been established in animals. The present study investigated the effect of different nutrients on intestinal dipeptidase, tripeptidase, carboxypeptidase (EC 3.4.12.-) and aminopeptidase N (ApN) (EC 3.4.11.2) activities in human fetuses and children. The effect of nutrients on isolated porcine kidney ApN was also studied. Sucrose, lactose and tributyrin had no effect on di-, tri-, and carboxypeptidase activities of mucosal homogenates, but tributyrin significantly (20-50%) inhibited both fetal and postnatal ApN activity in the small intestine and colon. The pH-independent inhibition of ApN is specific for tributyrin and to the product of its hydrolysis, butyric acid. Glycerol, triolein, and natural oils did not affect ApN activity. The inhibition of ApN by tributyrin was dose and time dependent and occurred in enterocyte brush border membranes as well as in the purified enzyme from porcine kidney. The kinetics of the purified ApN showed that the tributyrin effect is primarily competitive and associated mainly with an increase in K(m). These observations demonstrate the possibility of intestinal and kidney ApN regulation by lipids and products of their hydrolysis. We speculate that nutrient interactions arose quite early in the evolution and represent a mechanism for the regulation of food digestion.

Child↗
PubMed2002

Effect of tributyltin on adenylate content and enzyme activities of teleost sperm: a biochemical approach to study the mechanisms of toxicant reduced spermatozoa motility.

The effects of tributyltin (TBT) on the energy metabolism and motility of fish spermatozoa were investigated in vitro in African catfish and common carp. A significant (P<0.05) decrease of the duration and the intensity of motility was observed in catfish spermatozoa exposed to 0.27 microg/l TBT for 24 h. Exposure of catfish spermatozoa to 2.7-27 microg/l TBT caused an instant decrease in ATP content. In the presence of 27 microg/l TBT approximately 55% of the initial ATP concentration in catfish semen was lost after 60 min incubation while AMP concentrations increased and the total adenine nucleotide (TAN) pool remained unchanged. The reduction in sperm ATP levels could not be attributed to cell death since viability decreased only slightly over the period of exposure. In carp by contrast, none of the adenylates concentrations studied (ATP, ADP and AMP) were affected by TBT exposure at any experimental condition. However, carp sperm motility was significantly reduced by exposure to 2.7 microg/l TBT. Among the enzymes investigated only lactate dehydrogenase (LDH) in catfish sperm was significantly (P<0.01) affected by 27 microg/l TBT treatment with a reduction in activity of approximately 75%. Compared with carp sperm before TBT exposure, that of catfish had lower adenylate contents and overall lower enzymatic activities; this explains its slower sperm velocity and shorter duration of movement as measured by computer assisted sperm analysis (CASA). The present in vitro study shows that catfish spermatozoa are more sensitive to TBT exposure (and probably to other toxicants) than those of carp.

Adenine Nucleotides↗
PubMed2003

Quantitative determination of creatine kinase release from herring (Clupea harengus) spermatozoa induced by tributyltin.

Creatine kinase (CK, ATP creatine phosphotransferase, EC 2.7.3.2) is an enzyme participating in ATP regeneration, which is the primary source of energy in living organisms. We demonstrated that CK from herring spermatozoa has high activity ( approximately 452 micromol/min/g of fresh semen) and has a different electrophoretic mobility from isoenzymes present in skeletal muscle. In our study, we investigated toxic effect of tributyltin (TBT) on herring spermatozoa using a specific sperm viability kit to observe live and dead sperm cells with a confocal microscope. Treatment of herring spermatozoa with TBT caused a time-dependent decrease of viability: 35% nonviable cells with 5 microM TBT and more than 90% nonviable cells with 10 microM TBT after 6 h exposure. We also monitored CK release from damaged spermatozoa into surrounding medium containing different concentrations of TBT. The higher concentration of TBT was used the more CK release from spermatozoa was observed. We suggest that CK could be a good biomarker of sperm cell membranes degradation in the case when lactate dehydrogenase release from permeabilized cells is not possible for rapid determination of the effect of TBT.

Animals↗
PubMed1982

The effect of controlled release copper sulphate and tributyltin fluoride on the mortality and infectivity of Schistosoma mansoni cercariae.

Mortality and infectivity or Schistosoma mansoni cercariae were tested against various concentrations of controlled release copper sulphate (EC-8) and tributyltin fluoride (CBL-9B). The results indicate that survival of cercariae varied with concentrations of molluscicide and times of exposures. Statistical analysis reveals that LC50 and LC90 for EC-8 were 1.18 mg/l/hour and 1.82 mg/l/hour while LC50 and LC90 for CBL-9B were 16.8 microgram/l/hour and 21.7 microgram/l/hour respectively. Sublethal concentration of both molluscicides reduced cercarial infectivity considerably. The doses of 0.25 to 0.5 microgram/l/hour for EC-8 and 2.0 to 6.0 microgram/l/hour for CBL-9B were found to be sufficient to inhabit cercarial penetration of the host skin.

Animals↗
PubMed2002

Improvement of measurement precision of SPME-GC/MS determination of tributyltin using isotope dilution calibration.

A unique approach was developed to improve the precision of quantification of tributyltin (TBT) in sedimentsby solid phase microextraction (SPME) using isotope dilution GC/MS. The precision of the analytical technique was initially evaluated using standard calibration solutions. In selective ion monitoring (SIM) mode, the relative standard deviation (RSD) obtained for TBT based on peak area response was 18% (n = 11). When an internal standard, tripropyltin (TPrT), was used, the RSD decreased to 12%. A significant improvement in the precision using SPME was noted when a 117Sn-enriched TBT spike was employed; the RSD decreased 4-fold to 3%. Detection limits of 0.2 and 20 ng(Sn) L(-1) were achieved with SPME sampling and liquid-liquid extraction, respectively. Six analyses were performed for determination of TBT in PACS-2 sediment Certified Reference Material using both standard additions and isotope dilution procedures. For the latter, a 117Sn-enriched TBT spike was used. A concentration of 0.88 +/- 0.03 microg g(-1) (RSD 3.4%) obtained using standard additions was in good agreement with the certified value of 0.98 +/- 0.13 microg g(-1) as tin. Concentrations found using isotope dilution were 0.895 +/- 0.015 microg g(-1) (RSD 1.73%) as tin and 0.874 +/- 0.014 microg g(-1) (RSD 1.66%) as tin using a liquid-liquid extraction and SPME sampling, respectively. A 2-fold improvement in the precision of TBT concentration measurement using isotope dilution was clearly achieved, demonstrating its superiority in providing more accurate and precise results as compared to the method of standard additions. The isotope dilution technique eliminated the problem of poor reproducibility, which typically plagues SPME.

Calibration↗
PubMedDate not supplied

Radioiodination of antibodies via N-succinimidyl 2,4-dimethoxy-3-(trialkylstannyl)benzoates.

We have previously shown that use of N-succinimidyl 3-iodobenzoate (SIB) for radioiodination of monoclonal antibodies (MAbs) decreases the loss of radioiodine in vivo compared to MAbs labeled by using conventional methods. Herein, the synthesis of N-succinimidyl 2,4-dimethoxy-3-(trialkylstannyl)benzoates (alkyl = Me, Bu) are described as is their use as precursors for the radiosynthesis of N-succinimidyl 2,4-dimethoxy-3-iodobenzoate (SDMIB). A MAb F(ab')2 fragment labeled with SDMIB retained its ability to bind specifically to tumor homogenates. Paired-label tissue distribution studies indicate that the thyroid uptake (an indicator of deiodination) of hydrolyzed SDMIB was about 20 times that of hydrolyzed SIB. In contrast, thyroid uptake for SDMIB, when conjugated to a MAb, was only 1.4-2.8 times that for SIB and was considerably lower than levels reported in the literature for MAbs labeled by using direct, electrophilic iodination methods. Although MAbs labeled with SDMIB are significantly more inert to dehalogenation than those labeled by conventional methods, compared to the original SIB reagent, addition of two methoxy groups decreased retention of label in vivo.

Animals↗
PubMedDate not supplied

Assessment of radiochemical design of antibodies using an ester bond as the metabolizable linkage: evaluation of maleimidoethyl 3-(tri-n-butylstannyl)hippurate as a radioiodination reagent of antibodies for diagnostic and therapeutic applications.

Reduction of radioactivity levels in nontarget tissues such as the liver and kidney constitutes a problem to be resolved in diagnostic and therapeutic applications of radiolabeled monoclonal antibodies (mAbs). A new radioiodination reagent with an ester bond to liberate m-iodohippuric acid from covalently conjugated proteins, maleimidoethyl 3-(tri-n-butylstannyl)hippurate (MIH), was recently developed. MIH liberated m-iodohippuric acid from galactosylneoglycoalbumin in murine liver, and the radiometabolite was rapidly eliminated from the liver into urine as an intact structure. In this study, intact IgG and Fab fragment of a mAb against osteogenic sarcoma were radioiodinated with MIH to further assess the applicability of MIH to radioimmunoimaging and therapy. For comparison, a mAb radioiodinated with N-succinimidyl iodobenzoate (SIB) and indium-111 (111In)-labeled mAbs with diethylenetriaminepentaacetic dianhydride (cDTPA) or 1-[4-[(5-maleimidopentyl)amino]benzyl]-ethylenediaminetetraacetic acid (EMCS-Bz-EDTA) were used. Size-exclusion HPLC analysis and cell binding assays indicated the preservation of both structure and antigen binding affinity of radioiodinated MIH-OST7 (IgG). In biodistribution studies in mice, [125I]MIH-OST7 (IgG) showed faster systemic clearance of radioactivity after 24 h postinjection than did [131I]SIB- and [111In]EMCS-Bz-EDTA-OST7 (IgG). [125I]MIH-OST7 (IgG) also exhibited much lower radioactivity levels in nontarget tissues such as the liver and kidney, with higher radioactivity levels in the blood up to 72 h postinjection when compared with [111In]cDTPA-OST7 (IgG). Radioactivity excreted from the mice was found in the urine as m-iodohippuric acid, following administration of [125I]MIH-OST7 (IgG). In athymic mice bearing osteogenic sarcoma, [131I]MIH-OST7 (IgG) indicated higher tumor-to-nontarget ratios of radioactivity at both 24 and 48 h postinjection than [125I]SIB-OST7 (IgG). Although both radioiodinated OST7s showed similar radioactivity levels in the target at 24 h postinjection, a small but significant decrease in the target radioactivity level was observed with [131I]MIH-OST7 (IgG) at 48 h postinjection. In addition, [131I]MIH-OST7 (Fab) showed very rapid cleavage of the ester bond both in vivo and in vitro. These findings indicated that while MIH may be a useful reagent for radioimmunoimaging using IgG, mAb, its application to smaller molecular weight mAbs and radioimmunotherapy would be hindered due to the labile characteristics of the ester bond in plasma. Thus, while the present study reinforced the usefulness of metabolizable linkages for reducing nontarget radioactivity levels, a development of plasma-stable metabolizable linkages is also warranted for radioimmunotherapy and for smaller molecular weight polypeptides.

Animals↗
PubMedDate not supplied

Synthesis of 125I-labeled oligonucleotides from tributylstannylbenzamide conjugates.

A rapid and efficient method for the synthesis of 125I-labeled oligodeoxynucleotides ([125I]ODNs) is described. The key intermediates are tributylstannylbenzamide-modified ODNs (Sn-ODNs). Reaction conditions are described for the preparation of 5'-modified Sn-ODNs. Treatment with NaI and chloramine T gave conversion to the desired I-ODN, which was easily isolated by reversed phase chromatography. Thermal denaturation (Tm) studies showed that hybridization properties were not disturbed by the 4-iodobenzamide modification. An [125I]ODN was prepared and characterized by hybridization to 32P-labeled DNA targets. Sequence specific cleavage of the target DNA strand by 125I was measured.

Base Sequence↗
PubMed1983

Inactivation of yeast hexokinase B by triethyltin bromide and reactivation by dithiothreitol and glucose.

Binding of triethyltin bromide to yeast hexokinase B results in a rapid change in the reactivity of the sulfhydryl groups of the molecule. The change was characterized by an increased rate as well as extent of reaction of the -SH groups, and it preceded the onset of inhibition of the enzyme. Rapid gel filtration of the enzyme-triethyltin complex reversed this change in sulfhydryl reactivity, and when the eluted enzyme was subjected to short incubation periods, the slow inhibition that occurs with the unfiltered enzyme-triethyltin complex was no longer manifested. With prolonged incubation, however, the gel-filtered sample demonstrated increased rate of loss of enzyme activity, indicating that the gel filtration step did not completely reverse the effects of triethyltin on the enzyme. Active enzyme was recovered, following the inactivation of yeast hexokinase with triethyltin, by incubation of the inactivated enzyme with a large excess of glucose and dithiothreitol. Near total recovery of enzyme activity with reversion to native enzyme conformation was achieved following incubation at 35 degrees C of the enzyme with glucose and dithiothreitol each at 0.1 M. The possible involvement of either cysteine or histidine in the binding of triethyltin to the enzyme was probed, and it was concluded that neither of these amino acids are donor ligands for tin.

Dithiothreitol↗
PubMedDate not supplied

Exploring the scope of poly(ethylene glycol) (PEG) as a soluble polymer matrix for the Stille cross-coupling reaction.

The optimization and efficient parallel synthesis and purification of a library of biaryl, heterobiaryl, and styryl derivatives, via the first reported poly(ethylene glycol)-supported palladium-catalyzed Stille procedure, are described. Preliminary investigations into the reaction between monomethoxy poly(ethylene glycol)5000-supported iodide 1a with tributylphenyltin 2 revealed that the optimal "liquid-phase" conditions employ PdCl2(PPh3)2 (0.1 equiv) catalysis with LiCl (10 equiv) in DMF at 80 degrees C for either 48 h (at 20 mM concentration of 1a) or 24 h (at 10 mM concentration of 1a). The soluble polymer-supported reaction is superior to its solution-phase counterpart because the tributyltin side products and excess reagents are easily separated from the product intermediate 3a by precipitation of 3a into diethyl ether followed by recovery of the polymer by filtration in > 99%. In addition, the homocoupled byproduct 6 is also removed during this precipitation step. Under these conditions the transesterified biaryl adduct 4a can be isolated in 97-98% yield. The scope of this reaction was probed in a parallel format with the PEG-supported electrophiles 1a-b and a range of tributyl stannanes 2 and 7-13 under the optimized conditions vide supra. Subsequent cleavage of the polymer-supported adducts, by transesterification, and short column chromatography yielded a library of substituted methyl benzoates 4a-b and 14a-b to 20a-b in high yield (69-99%) and purity (> 95%).

Catalysis↗
PubMed2005

New model calculations of pH-depending tributyltin adsorption onto montmorillonite surface and montmorillonite-rich sediment.

Interactions of the pollutant tributyltin (TBT) with mineral surfaces affects its distribution and transport in aqueous systems. In the present work, model calculations are reported that quantify TBT adsorption onto pure-phase montmorillonite (sample SWy) under various pH and salinity conditions that are important from an environmental perspective. The pH level in the system is of substantial interest because it affects the speciation of TBT in solution as well as the surface properties of the solid phase, which are both important for adsorption reactions. The model is based on the generalized diffused layer model that includes >X- sites in order to account for the cation exchange effects of TBT attraction. The presence of >AIOH and >SiOH sites atthe mineral surface was not considered separately during calculation. Instead, nonselective sites (>SOH) versus selective sites (>SsOH) were distinguished with respect to the sorptive sites on montmorillonite. The latter are characterized by a high affinity of TBT bonding. Both sorptive sites exhibit the same protolysis constants but different TBT binding constants [logK(TBT/2) = -1.18 for (>SOH), logK(TBT/1) = 3.98 for (>SsOH)]. LogK(X/TBT) for the cation exchange reaction was determined as between 3.05 and 4.14. The results indicate that the inclusion of selective sites during calculations is essential for quantifying pH-dependent TBT adsorption successfully. The parameters determined for the TBT adsorption onto pure-phase montmorillonite were subsequently used to calculate pH-dependent TBT adsorption onto a natural montmorillonite-rich sediment.

Adsorption↗