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PubMedDate not supplied

Nonhuman primates in behavioral toxicology: issues of validity, ethics and public health.

The small, but vital, niche of nonhuman primates in neurotoxicology is examined. Several models of sensory and cognitive function have been especially useful with primates. Their sensitivity to low doses is clear. The validity of data from these models is indicated by their high correlation with data from intoxicated and normal humans, by the degree to which they approximate job functions and other vital human performances, and by their ability to document specific changes in behavioral function which correlate well with morphological and biochemical effects. The use of primates for this research is justified by the absence of adequate alternatives using nonprimate species, in vitro tests or computer programs. A series of experiments on the effects of methylmercury is used to illustrate ethical and scientific issues concerning research with primates. Recent trends are illustrated by data with trimethyltin.

Animal Experimentation↗
PubMed1988

A comparison of the rates of methylation of mercury(II) species in aquatic media by various organotin and organosilicon moieties.

Metals can be methylated in environmental aqueous media by a variety of organotin and organosilicon compounds. Main group metals and metalloids were surveyed for the identification of species that can either donate or accept methyl groups. The methylation of mercury(II) by trimethyltin cation was found to be a bimolecular reaction, the reaction rate of which decreased with increasing chloride concentration. Kinetic investigations using NMR techniques showed that the most important pairs of reactants were (CH3)3Sn+ + HgCl2, (CH3)3SnCl + HgCl2, and (CH3)3SnCl + HgCl-3. Sodium 2,2,3,3-tetradeutero-3-(trimethylsilyl)propionate (TSP) and sodium 2,2-dimethyl-2-silapentane-5-sulfonate (DSS) were found to methylate mercury(II). Organylsilatranes were found to transfer their organic groups readily to mercury(II) to produce organomercury compounds.

Magnetic Resonance Spectroscopy↗
PubMed1996

The structure of organometals determines cytotoxicity and alteration of calcium homeostasis in HL-60 cells.

There is increasing concern about the degradation and metabolisation as well as the biochemical mechanisms of action of organometallic compounds. They are known to be immunotoxic and/or neurotoxic. Because of their different toxic capacities, the development of a reliable correlation between molecular parameters and biochemical effects, which could be helpful in risk assessment, was an aim of this study. The tested organolead and -tin compounds decrease the viability of human cells in culture in a time- and concentration-dependent manner. Parabolic QSAR(1)(1) The abbreviations used are: TMT, trimethyltin chloride; TET, triethyltin bromide; TPT, tripropyltin chloride; TBT, tri- n-butyltin chloride; DBT, di- n-butyltin dichloride; TEL, triethyllead chloride; DEL, diethyllead dichloride; TML, trimethyllead chloride; TPhL, triphenyllead chloride; QSAR, quantitative structure-activity relationships; TSA, total surface area; MW(ion), ionic molecular weight; fMLP, N-formyl-L-methionyl-L-leucyl-L-phenylalanine; fluo-3, fluo-3 free acid; fluo-3 AM, fluo-3 acetoxymethyl ester; Me(2)SO, dimethyl sulfoxide; PLA(2), phospholipase A(2) (EC 3.1.1.4); FCS, fetal calf serum; HEPES, 4-(2-hydroxy-ethyl)-1-piperazineethanesulfonic acid; EGTA, [ethylene-bis(oxyethylenenitrilo)]tetraacetic acid; [Ca(2+)](i), cytosolic free Ca(2+) concentration models yield an adequate correlation between toxicity expressed as LC(50) and structural parameters like ionic molecular weight (MW(ion)) or total surface area (TSA). Two main chemical attributes of the organometals are probably responsible for such a parabolic relationship: the hydrophobic side chain and the polar metal atom. Furthermore, all tested organometal compounds evoke a persistent increase of the cytosolic free calcium concentration [Ca(2+)](i). This effect is mainly due to an influx from the extracellular space. Further results suggest that Ca(2+) enters the cell via opened calcium channels. Based on the essential role of Ca(2+) within cellular signalling, the perturbation of calcium homeostasis appears to be an important event in final cell killing by organometals and it is most likely that other biochemical mechanisms, e.g. activation of phospholipase A(2), are possibly mediated by an increase of [Ca(2+)](i).

Journal Article↗
PubMed2000

Trimethylsilyl- and trimethylstannyldimethylphosphane--convenient and versatile reagents for the synthesis of polyfluoroaryldimethylphosphanes.

Trimethylsilyldimethylphosphane (Me3SiPMe2) and the corresponding tin compound (Me3SnPMe2) were used as reagents for the substitution of fluorine by the Me2P group in polyfluoroarenes C6F5X (X = F, H, Cl, CF3) and C5NF5. The reactions occur even under mild conditions (T = 0-20 C), either in benzene or without solvent, to give as a rule 4-X-1-(dimethylphosphano)tetrafluorobenzenes (XC6F4PMe2, 1-4) and 4-(dimethylphosphano)tetrafluoropyridine (C5NF4PMe2, 5), respectively, in yields between 75 and 95%. In the case of C6F6, double substitution is also observed, which affords 1,4-bis(dimethylphosphano)tetrafluorobenzene (6). A very efficient route to the compounds XC6F4PMe2 (X = F, H, Cl, CF3) and C5NF4PMe2 was developed as a one-pot reaction of the corresponding fluoroarenes with tetramethyldiphosphane (P2Me4) and trimethyltin hydride (Me3SnH) at moderate temperatures. This process was tested for C6F6 and perfluorobiphenyl which gave C6F5PMe2 (1) and 4,4'-bis(dimethylphosphano)octafluorobiphenyl (7), respectively. The results, which included kinetic measurements that used the intensities of the 31P signals, revealed the influence of the substrate type on the rate of reaction in the sequence: C5NF5>C6F5CF3> C6F5Cl, C6F5PMe2>C6F5H>C6F6>> C6H5F. Ab initio calculations were carried out on the model reactions of pentafluoropyridine with silylphosphane, phosphane or phosphide to discriminate between possible reaction mechanisms. The novel phosphanes were characterised by spectroscopic investigations (NMR, MS), by preparation of the related thiophosphanes ArFP(=S)Me2 (8-14), their spectroscopic and analytic data and single crystal X-ray diffraction studies on five of these derivatives.

Journal Article↗
PubMed1992

Cytotoxicity of tin on human peripheral lymphocytes in vitro.

The comparative effects of inorganic and organic tin compounds on chromosomes were assessed in human peripheral blood lymphocytes of healthy donors 20-40 years of age. The endpoints observed were chromosomal abnormalities, sister-chromatid exchanges (SCEs) and cell cycle kinetics. The maximum concentrations which reduced the replicative index by about 50%, of stannic chloride and trimethyltin chloride were 40 micrograms and 2 micrograms per culture respectively. The tested doses were 20 micrograms and 10 micrograms of stannic chloride and 1 microgram and 0.5 microgram of trimethyltin chloride. Both doses of stannic chloride induced a much higher frequency of chromosomal abnormalities (P less than 0.05-P less than 0.001) and a greater reduction of cell cycle kinetics than the corresponding relative doses of trimethyltin chloride. The frequencies of SCEs/cell induced by the latter were, however, slightly higher than those induced by the former.

Cell Cycle↗
PubMed1986

Triorganotin-induced cytotoxicity to rat thymus, bone marrow and red blood cells as determined by several in vitro assays.

To further investigate the immunotoxic effects of tri-n-propyltin chloride (TPTC), tri-n-butyltin chloride (TBTC) and triphenyltin chloride (TPhTC) several cytotoxicity tests with a series of trialkyltin chlorides and TPhTC were carried out, using isolated rat thymocytes as target cells. Thymocytes, cultured in a serum-supplemented medium, were exposed to organotin concentrations ranging from 0.01 to 10 microM for periods up to 30 h. Parameters such as cell count, trypan blue exclusion, chromium release, thymidine incorporation and cyclic AMP production were used to evaluate the cytotoxicity of these compounds. The more lipophilic compounds TPTC, TBTC, tri-n-hexyltin chloride (THTC) and TPhTC appeared most cytotoxic, reducing thymidine incorporation at concentrations as low as 0.05-1 microM. Membrane damage as determined by trypan blue exclusion and chromium release occurred at higher levels (1-10 microM). The water soluble homologue trimethyltin chloride (TMTC) was least effective in all test models. When phosphate-buffered saline supplemented with glucose was used as incubation medium, TBTC appeared more cytotoxic to thymocytes. Using this medium in 5-h incubations the cytotoxicity of TBTC to thymus, bone marrow and red blood cells was compared. Bone marrow cells were slightly less sensitive than thymocytes, while red cells were relatively resistant. In conclusion, of the triorganotin compounds especially the lipophilic homologues are cytotoxic in vitro.

Animals↗
PubMed1999

Differential gliotoxicity of organotins.

On the basis of reports that astrocytes play an important role in the neurotoxicity of trimethyltin (TMT), we investigated the sensitivity of astrocytes to TMT and compared it to triethyltin (TET), a neurotoxic analog with a different in vivo specificity. The gliotoxicity of these two compounds was further compared to that of tributyltin (TBT) and triphenyltin (TPT), two purportedly nonneurotoxic organotin compounds. The time and concentration components of organotin toxicity were determined by measuring lactate dehydrogenase (LDH) release and formazan production from dimethylthiazolyldiphenyltetrazolium bromide (MTT). A TMT concentration of 100 micromol/L did not elevate extracellular LDH until 48 h after exposure, while signs of toxicity were not seen at 72 h for concentrations less than 10 micromol/L. Extracellular LDH activity increased 24 h after exposure to concentrations of TET, TBT, and TPT as low as 2.5 micromol/L. TMT was the only organotin to produce a delayed cytotoxicity, requiring both higher concentrations and more time to produce discernible toxicity. In contrast with TBT and TPT, the toxicity of the two neurotoxic organotins (TMT and TET) produced an early increase in MTT reduction. The distinct pattern of toxicity for TMT does not explain its selective in vivo toxicity, but the lack of sensitivity of astrocytes to this organotin also does not rule out more subtle changes in these cells that could disrupt normal glial/neuronal interactions.

Animals↗
PubMed1992

The genotoxicity of organotin compounds in SOS chromotest and rec-assay.

In these days pollution by organotin compounds in the environment extends widely and effects on human health are feared. We studied the genotoxicity of various organotin compounds (butyltins, phenyltins, methyltins) and inorganic tin (SnCl4), which are present in the environment, with the SOS chromotest and the rec-assay. Mono-n-butyltin oxide, n-butyltin trichloride and di-n-butyltin dichloride showed high SOS-inducing potency in the SOS chromotest with Escherichia coli PQ37. Di-n-butyltin dichloride, tri-n-butyltin chloride, bis(tri-n-butyltin)oxide, dimethyltin dichloride and trimethyltin chloride were recognized as genotoxic chemicals by the rec-assay.

4-Nitroquinoline-1-oxide↗
PubMed1988

Interactions of neurotoxicants with neurotransmitter systems.

Many neurotoxic compounds have been shown to interfere with neurotransmission both in vitro and following acute and chronic administration. Various parameters of neurotransmission can be directly affected by neurotoxicants; these include the enzyme(s) synthesizing a neurotransmitter, the release and uptake processes, the enzyme(s) which metabolize the neurotransmitter, the receptors, and post-synaptic events associated with receptor activation. Some neurotoxicants can interfere with neurotransmission indirectly, by interacting for example with energy metabolism, sodium channels or ATPases. Furthermore, measured alterations of any parameter of neurotransmission can be the result of neuronal death, due to a cytotoxic effect of the neurotoxicants. Chemicals which have been shown to alter neurotransmission include solvents (e.g. carbon disulfide), metals and organometals (e.g. lead, mercury, trimethyltin) and pesticides (e.g. organophosphates, pyrethroids, organochlorines, formamidines). An example of the various alterations in neurotransmitter parameters, which can occur following acute or chronic administration, is represented by the organophosphates. Organophosphorus insecticides owe their acute toxicity to inhibition of acetylcholinesterase and accumulation of acetylcholine at cholinergic receptors. Chronic exposure to these compounds results in the development of tolerance to their toxicity which is associated with a decrease in the density of muscarinic and nicotinic receptors in both the central and peripheral nervous system. Other examples of the interactions of neurotoxicants with neurotransmitters are also described.

Nervous System↗
PubMed1983

Inhibitory effect of triethyltin on taurine transport by glioma cells.

The effects of triethyltin (TET) on the transport of taurine, glutamate, lysine, Na+, K+ (using 86Rb+ as tracer), and Cl- by LRM55 glioma cells were examined. Taurine transport was inhibited by TET at much lower concentrations (IC50 = 2.5 microM) than either glutamate or lysine transport (135 and 110 microM, respectively). TET had no significant effect on Na+, Cl-, or 86Rb+ influx at the low concentrations greater than 100 microM. The failure of low concentrations (less than or equal to 10 microM) of TET to affect ion transport indicated that inhibition of taurine transport was not secondary to effects of TET on ion movements or gradients. This conclusion was supported by the observation that neither ouabain nor furosemide, which do affect ion movement and gradients, strongly inhibited taurine transport. Uncouplers and inhibitors of oxidative phosphorylation (cyanide, 2,4-dinitrophenol, and carbonyl cyanide-m-chlorophenyl hydrazone) also had only small effects on taurine transport, suggesting that inhibition by TET was not secondary to possible effects on oxidative phosphorylation. TET had no effect on the efflux of taurine from LRM55 cells at the low concentrations that inhibit uptake, but it induced a nonspecific increase in membrane permeability at much higher concentrations (greater than 100 microM). Tri-n-propyltin and tri-n-butyltin were also potent inhibitors of taurine transport (IC50 = 2.3 and 11 microM, respectively), but trimethyltin was much less potent (144 microM).

Biological Transport↗
PubMed1990

Tin compounds in sediments of Lake Maryut, Egypt.

Concentrations of inorganic, methyl- and butyltin compounds were quantified by a hydride derivatization/atomic absorption technique for eleven short sediment cores sampled from Lake Maryut, Alexandria, Egypt. All samples contained inorganic Sn concentrations ranging from 1875 to 8190 ng g(-1) dw, the highest levels occurring in the eastern portion of the lake. Methyltin concentrations were also highest in the eastern lake, decreasing considerably in the western lake. Mono- and dimethyltins were found at all sites, the former species being the highest in concentration. Trimethyltin was much lower than either, and was absent from four out of 11 sites. An opposite trend was observed for the butyltin species, their concentration being highest in the west lake, decreasing eastward. Mono- and dibutyltin were almost equal in concentration. Although tributyltin was absent from one site in the lake, it was much higher in concentration than the two other species, particularly in the western lake. In general, methyl- and butyltin concentrations decreased with depth in the cores. Methyltin compounds appear to form within the lake mainly by methylation of inorganic Sn, and butyltin compounds are derived from anthropogenic sources. No significant correlations were found between organic C and concentrations of methyltin species. A significant negative correlation was found between total butyltin concentrations and organic C in surficial sediments.

Journal Article↗
PubMed1986

Influence of organotins on rat platelet aggregation mechanisms.

The effects of ten organotins on rat platelet aggregation mechanisms were examined. Bis(tri-n-butyltin)oxide was the most potent inhibitor of both ADP- and collagen-induced aggregation, and it was the only organotin that directly induced aggregation. It also increased the latent period for induction of aggregation by collagen. Triphenyltin hydroxide was a weak inhibitor of both ADP- and collagen-induced aggregation. However, in contrast to bis(tri-n-butyltin)oxide, it decreased the latent period for collagen-induced aggregation. A similar effect also was observed with diphenyltin dichloride, phenyltin trichloride, and cyhexatin. Tri-n-butyltin chloride and tetra-n-butyltin demonstrated specificity in their action since aggregation induced by ADP but not collagen was inhibited. Tri-n-propyltin chloride, trimethyltin chloride, and fenbutatin oxide were without discernible effect on rat platelet aggregation.

Adenosine Diphosphate↗
PubMed1991

Triorganotins inhibit the mitochondrial inner membrane anion channel.

The inner membrane of liver and heart mitochondria possesses an anion uniport pathway, known as the inner membrane anion channel (IMAC). IMAC is inhibited by matrix Mg2+, matrix H+, N,N'-dicyclohexycarbodiimide, mercurials and amphiphilic amines such as propranolol. Most of these agents react with a number of different mitochondrial proteins and, therefore, more selective inhibitors have been sought. In this paper, we report the discovery of a new class of inhibitors, triorganotin compounds, which block IMAC completely. One of the most potent, tributyltin (TBT) inhibits malonate uniport via IMAC 95% at 0.9 nmol/mg. The only other mitochondrial protein reported to react with triorganotins, the F1F0ATPase, is inhibited by about 0.75 nmol/mg. The potency of inhibition of IMAC increases with hydrophobicity in the sequence trimethyltin much less than triethyltin much less than tripropyltin less than triphenyltin less than tributyltin; which suggests that the binding site is accessible from the lipid bilayer. It has long been established that triorganotins are anionophores able to catalyze Cl-/OH- exchange; however, TBT is able to inhibit Cl- and NO3- transport via IMAC at doses below those required to catalyze rapid rates of Cl-/OH- exchange. Consistent with previous reports, the data indicate that about 0.8 nmol of TBT per mg of mitochondrial protein is tightly bound and not available to mediate Cl-/OH- exchange. We have also shown that the mercurials, p-chloromercuribenzene sulfonate and mersalyl, which only partially inhibit Cl- and NO3- transport can increase the IC50 for TBT 10-fold. This effect appears to result from a reaction at a previously unidentified mercurial reactive site. The inhibitory dose is also increased by raising the pH and inhibition by TBT can be reversed by S2- and dithiols but not by monothiols.

4-Chloromercuribenzenesulfonate↗
PubMed1995

Organotin compounds induce calcium overload and apoptosis in PC12 cells.

We examined the effects of four tri-substituted organotin compounds on intracellular Ca2+ and survival in PC12 cells. Treatment with micromolar concentrations of tributyltin and triphenyltin caused a rapid increase in the cytosolic free Ca2+ concentration ([Ca2+]i). This was due to enhanced Ca2+ influx and release from intracellular stores. When the [Ca2+]i elevation was maintained for over 30 min, internucleosomal DNA cleavage typical of apoptotic cell death followed. In contrast, when the increase in [Ca2+]i was transient, cells did not show internucleosomal DNA cleavage and retained their viability. Triethyltin modified [Ca2+]i only slightly, whereas trimethyltin had no effect. The latter two agents did not modify cell viability. Our data suggest that the toxicity of organotins in PC12 cells is linked to their ability to promote intracellular Ca2+ overload, which triggers apoptosis.

Animals↗
PubMed1989

Flow cytometric comparison of the effects of trialkyltins on the murine erythroleukemic cell.

Cellular effects of exposure to tributyltin (TBT), triethyltin (TET), or trimethyltin (TMT) were investigated by flow cytometry employing the murine erythroleukemic cell (MELC) as a model cellular system. Cell viability was investigated by the carboxyfluorescein diacetate (CFDA) uptake/propidium iodide (PI) exclusion method: above a critical concentration (exposure for 4 h), which was specific for each of the trialkyltin compounds, the cell becomes permeable to PI, indicating loss of viability. Cellular CF fluorescence (derived from intracellular hydrolysis of CFDA) increased as a function of alkyltin concentration below the critical concentration and decreased as viability decreased above the critical concentration. Relative membrane potential, monitored with a cyanine dye (DiOC6), correlated with viability (PI exclusion), remaining essentially unaltered below the critical concentration and decreasing above it. At/above 1 microM TBT, 5 microM TET, or 100 microM TMT, the cell cycle was blocked in the G2/M phase. The 90 degrees light scatter (a measure of refractive index), axial light loss (a measure of volume), and fluorescein isothiocyanate (FITC) fluorescence (a measure of protein content) of nuclei isolated from trialkyltin-treated MELC by detergent treatment, increased as a function of organotin dose. Fluorescence and interference microscopy revealed increased quantities of residual cytoplasmic tags adherent to the nuclei as a function of organotin dose, apparently resulting from increased cytoplasmic resistance to detergent-mediated solubilization. The effects of the trialkyltins correlated with their lipophilicity (octanol/water coefficient). These data support the hypothesis that fixation (protein denaturation, cross-linking, etc.) is an important mode of organotin cytotoxicity.

Animals↗
PubMed1971

Oxidative phosphorylation. The relation between the specific binding of trimethylytin and triethyltin to mitochondria and their effects on various mitochondrial functions.

1. A binding site (site 1) is present in mitochondria with affinity for trimethyltin and triethyltin adequate for a site to which they could be attached when the processes of energy conservation are inhibited. 2. The quantitative relationships between the binding of trimethyltin and triethyltin to site 1 and their effects on various mitochondrial functions have been examined. 3. ATP synthesis linked to the oxidation of pyruvate, succinate and intramitochondrial substrate, ATP synthesis and oxygen uptake (succinate or pyruvate as substrate) stimulated by uncoupling agents are all inhibited by trimethyltin and triethyltin; when inhibition is less than 50% the ratio (percentage inhibition)/(percentage of binding site 1 complexed) is approx. 10:1. 4. ATP synthesis linked to the oxidation of reduced cytochrome c (ascorbate+NNN'N'-tetramethyl-p-phenylenediamine), ATP hydrolysis and oxygen uptake in the presence of low concentrations of trimethyltin and triethyltin approach zero activity as the proportion of binding site 1 complexed approaches 100%. 5. Possible interpretations of these findings are discussed with reference to published arrangements for coupling of electron transport to ATP synthesis and also to our present knowledge of the chemical and biological specificity of trialkyltin compounds.

Adenosine Triphosphate↗
PubMed1986

Effects of various inhibitors of oxidative phosphorylation on energy metabolism, macromolecular synthesis and cyclic AMP production in isolated rat thymocytes. A regulating role for the cellular energy state in macromolecular synthesis and cyclic AMP production.

Inhibitors of oxidative phosphorylation such as several triorganotin compounds, oligomycin, 2,4-dinitrophenol and carbonylcyanide p-trifluoromethoxyphenylhydrazone suppress energy metabolism of isolated rat thymocytes as indicated by a reduction of ATP levels, an increase in glucose consumption and by a marked accumulation of lactate. Also these compounds effectively inhibit the incorporation of DNA, RNA and protein precursors into acid-precipitable material of thymocytes. Moreover, the prostaglandin E1-induced elevation of cAMP is markedly reduced by these inhibitors. A correlation is observed between the effects on energy metabolism, macromolecular synthesis and cAMP production, since from a series of trialkyltin chlorides, tri-n-propyltin, tri-n-butyltin and tri-n-hexyltin are very effective inhibitors of these functions, while trimethyltin and tri-n-octyltin affect neither of them; other inhibitors of oxidative phosphorylation, each of them with quite different mechanisms of action, also inhibit macromolecular synthesis and cAMP production. The finding that a rise in intracellular ATP concentrations leads to a reversion of the tri-n-butyltin-induced inhibition of cAMP production and uridine incorporation, indicates a regulating role for the cellular energy state in these aspects of cellular function.

2,4-Dinitrophenol↗
PubMed1975

The decrease of mitochondrial substrate uptake caused by trialkyltin and trialkyl-lead compounds in chloride media and its relevance to inhibition of oxidative phosphorylation.

1. In a 100 mM-KCl medium (pH 6.8) containing ATP, triethyltin (1 muM) causes a decrease in the uptake of pyruvate, malate, citrate or beta-hydroxybutyrate by rat liver mitochondria, but no decrease is observed in a 100 mM-KNO3 medium. This response is not modified by the presence of rotenone in the incubation medium. 2. In the KCl medium at least 1 muM-triethyltin is required to cause maximum inhibition of pyruvate uptake. 3. Trimethyltin, tributyltin and the trialkyl-lead analogues at 1 muM, to varying degrees, also cause a decrease in pyruvate uptake by mitochondria only in the KCl medium. 4. Triethyltin stimulates resting respiration of mitochondria with all the substrates tested in the KCl medium but not in the KNO3 medium, yet this stimulation of O2 uptake occurs under conditions when substrate uptake is decreased. 5. In contrast, both O2 uptake during state 3 respiration and ATP synthesis when linked to the oxidation of pyruvate, malate or citrate are strongly inhibited by 1 muM-triethyltin in a KCl medium, but O2 uptake and ATP synthesis during the oxidation of beta-hydroxybutyrate are only slightly affected. In a KNO3 medium O2 uptake and ATP synthesis linked to the oxidation of all substrates are only slightly affected. 6. The relevance of the decrease in substrate uptake by mitochondria caused by triethyltin in a KCl medium to the greater sensitivity of various mitochondrial functions observed in vitro is discussed. It is concluded that decrease of matrix substrate content is probably not the major cause of the greater sensitivity of oxidative phosphorylation to triethyltin in a KCl medium observed previously.

Adenosine Triphosphate↗