Di-n-butyltin Dichloride Research Articles

Identification by DNA Macroarray of nur77 as a Gene Induced by Di-n-butyltin Dichloride: Its Role in Organotin-Induced Apoptosis

The thymotoxic organotin compounds di-n-butyltin dichloride (DBTC) and tri-n-butyltin chloride (TBTC) are known to induce apoptosis in vitro in rat thymocytes. They also affect macromolecular synthesis, inhibiting DNA synthesis and increasing RNA synthesis. Since these RNA molecules, likely to be involved in the initiation of the apoptotic process, have not been identified yet, the purpose of this research was to characterize by a cDNA macroarray the expression of genes involved in DBTC-induced apoptosis. We found that nur77 was rapidly transcripted in vitro following exposure of freshly isolated rat thymocytes to 3 μM DBTC. nur77 induction has also been observed in vivo after treatment of rats with apoptotic doses (60 mg/kg body wt) of DBTC. The products of nur77 are known to be involved in the apoptotic process, as nur77 is a transcription factor expressed in response to T-cell receptor-mediated apoptosis in immature T cells. Antisense oligonucleotide inhibition of nur77 expression prevented apoptosis induced by DBTC, supporting a role for nur77 in organotin-induced apoptotic cell death.

Organotin-induced apoptosis occurs in small CD4 +CD8 + thymocytes and is accompanied by an increase in RNA synthesis

The organotin compounds di- n-butyltin dichloride (DBTC) and tri- n-butyltin chloride (TBTC) induce thymus atrophy in rats. At low doses they inhibit immature thymocyte proliferation, whereas at higher doses in particular TBTC induces apoptotic cell death. In vitro, a similar concentration–effect relationship was observed, i.e. low concentrations inhibit DNA and protein synthesis and higher concentrations induce apoptosis. The mechanism of apoptosis by organotins has been partly investigated, but their capacity to inhibit protein synthesis seems to contradict with the idea that macromolecular synthesis is required for organotin-induced apoptosis. Therefore, we aimed to evaluate the relation between apoptosis and the synthesis of RNA and proteins, with a focus on the apoptosis-sensitive thymocyte subset. Results showed that DBTC increases RNA synthesis in particular in the subset of small CD4 +CD8 + thymocytes, which normally shows a high incidence of DNA fragmentation. Moreover, the RNA synthesis inhibitor actinomycin D or the protein synthesis inhibitor cycloheximide protected cells from apoptosis by DBTC or TBTC. Although organotin compounds increase synthesis of the heat shock protein HSC73/HSP72, heat shock treatment did not initiate apoptosis in thymocytes, neither antagonized organotin-induced apoptosis. This indicates that synthesis of heat shock proteins is not related to organotin-induced increase of RNA synthesis, and that other RNA-molecules are probably involved.

Electron Microscopic Detection of Tin Accumulation in Biliopancreatic Concrements after Induction of Chronic Pancreatitis in Rats by Di- n -butyltin Dichloride

The organotin compound di- n -butyltin dichloride (DBTC) is able to induce an acute and later a chronic pancreatitis in rats. In previous papers the authors demonstrated this DBTC pancreatitis as a rat model for an interstitial pancreatitis with tendency to transduction to the chronic form. DBTC is excreted according to its lipophilic nature by liver and bile. Therefore, the bilio-pancreatic main duct is necrotized by the tin-loaded bile. The duct system is blocked by cell debris and later by epithelial proliferations. In the chronic phase, numerous rats develop concrements in the main duct. In the present paper, the authors report about bacterial growth in some bilio-pancreatic concrements. Whereas the electron microscopic detection of tin by energy-dispersive X-ray analysis (EDX) in SEM or electron energy loss spectroscopy (EELS) in TEM was negative in the parenchyma of pancreas and liver, some concrements with bacterial cells were positive for this element. Tin mapping with energy spectroscopic imaging (ESI) in TEM demonstrated the congruency of tin signals and electron-dense particles inside these bacteria and of electron-dense accumulations in the matrix of these concrements. The low content of tin in pancreatic and liver tissue and the higher quantity of tin inside the bacterial contaminated concrements were supported by atomic absorption spectrophotometry (AAS). The paper discusses the long time preservation of tin in the concrements as an action of heavy-metal-accumulating bacteria, which should be classified in the future by bacteriological methods.

Repeated administration of a mild acute toxic dose of di-n-butyltin dichloride at intervals of 3 weeks induces severe lesions in pancreas and liver of rats.

Di-n-butyltin dichloride (DBTC) induced thymus atrophy, bile duct lesions, pancreatitis, and liver lesions in rats. Depending on dose [6 and 8 mg/kg intravenous (i.v.) DBTC] and time (1-24 weeks), the lesions in pancreas developed to a pancreatic fibrosis and the lesions in liver to liver cirrhosis. A single i.v. administration of 4 mg/kg DBTC induces a mild interstitial pancreatitis after 2-4 days followed by a restitutio ad integrum after 21-28 days. In the present study, the lesions of biliopancreatic duct, pancreas, and liver of rats after repeated administration of 4 mg/kg DBTC i.v. at intervals of 3 weeks have been investigated. The histopathological changes of pancreas and liver were examined by light microscopy 1,4, and 7 days and 2,3,4,6,9, and 12 weeks after administration of DBTC. Furthermore, pathobiochemical parameters of pancreatitis (amylase and lipase activity in serum), liver lesions (alkaline phosphatase activity and bilirubin in serum), and of fibrosis (hyaluronic acid in serum) were studied. Repeated administration of rats with DBTC (4 mg/kg i.v.) at intervals of 3 weeks induced an acute interstitial pancreatitis and after 9-12 weeks, a pancreatic fibrosis and liver lesions (intrahepatic bile duct hyperplasia, inflammation in periportal tract, and necrosis). In serum, elevated levels of alkaline phosphatase, bilirubin, and hyaluronic acid were found. This study demonstrates that the organotin compound induces toxic effects on pancreas and liver of rats by repeated administration of lower doses at long intervals. The risk of exposure to organotin at long intervals should be considered.

Effects of endocrine disrupting chemicals on the microtubule network in Chinese hamster V79 cells in culture and in Sertoli cells in rats

The effects of ten endocrine disrupting chemicals, i.e., bisphenol A (BPA), p-nonylphenol (NP), p-octylphenol (OP), p-pentylphenol (PP), butyl benzyl phthalate (BBP), dicyclohexyl phthalate (DCHP), di-n-butyl phthalate (DBP), tetrabutyltin (TBT), tri-n-butyltin chloride (TBC), and di-n-butyltin dichloride (DBD), as well as 17 beta-estradiol (E(2)) as a positive control on the microtubule network in Chinese hamster V79 cells in culture were examined by the indirect immunofluorescence method using anti-beta-tubulin antibody. In the whole-animal system, the effects of BPA, NP, OP, BBP, DBD, and E(2) as well as vinblastine sulfate (VB) as a positive control on microtubules in the cytoplasm of Sertoli cells in rats were examined by electron microscopy. In Chinese hamster V79 cells, TBC and DBD showed higher microtubule-disruptive activity than E(2), while other chemicals had less activity than E(2). The ranking for efficiency on microtubule disruption was (TBC falling dots DBD) > (E(2) = TBT) > (BPA = alkylphenols, NP and OP) >> (phthalate esters, BBP, DHP, and DBP). In rats as a whole-animal system, no disrupting effects on the microtubule network in the cytoplasm of Sertoli cells were observed under any environmental chemicals tested, whereas exposure to VB resulted in marked disruption of the microtubule network. The results of this study suggested that some endocrine disrupting chemicals have disrupting effects on the microtubule network in vitro, but no such effects in vivo.

Potential teratogenicity of di-n-butyltin dichloride and other dibutyltin compounds.

The developmental toxicity of di-n-butyltin dichloride (DBT-dC) was evaluated in Wistar rats following oral administration. No maternal toxicity, embryotoxicity, or malformations were observed at 1, 2.5, or 5 mg DBT-dC/kg body weight. Signs of maternal toxicity, including decreased food consumption, body weight gain, and thymus weight, were observed at 10 mg/kg body weight DBT-dC. At this dose, no evidence of embryotoxicity, including such measures as total resorptions, viable fetuses, or fetal weights, was noted in any litter data. There was a slightly increased frequency of total malformations at the 10 mg/kg dose level of 4/262 treated vs. 1/269 control fetuses. All defects occurred singly with no clustering nor organ system pattern of occurrence, which would be indicative of a teratogenic effect. The no-observed-adverse-effect-level (NOAEL) for prenatal as well as maternal toxicity was considered to be 5 mg DBT-dC/kg body weight. The interpretation and utility of previously published studies on the developmental toxicity of dibutyltin compounds are confounded by dose regimen and data reporting deficiencies. These studies suggest that, after oral administration during days 6-17 of pregnancy, the NOAEL for malformations in rats of different strains ranges from 1.7 to 5 mg/kg body weight. In these studies, the maternal LD50 was reported to be about 8 mg/kg body weight in one study but at greater than 15 mg/kg in others. Thus, the NOAEL for teratogenicity may be roughly estimated to be from one-tenth to one-third of the maternal LD50. When evaluated, thymus involution, a typical but reversible effect of di- and tri-butyltin compounds, was also observed at 5-10 mg/kg body weight. The most susceptible time for inducing teratogenic effects is reported to be days 7-9 of pregnancy, but malformations have also been found with dosing over longer duration at lower doses. It is doubtful that the findings of malformations at highly toxic doses in animals has any health hazard significance, especially when human exposure to dibutyltins typically occurs at several orders of magnitude lower than the doses used in these studies. Further comparative pharmacokinetic studies would be necessary in order to refine the hazard characterization.

Organotins Induce Apoptosis by Disturbance of [Ca2+]i and Mitochondrial Activity, Causing Oxidative Stress and Activation of Caspases in Rat Thymocytes

Di-n-butyltin dichloride (DBTC) and tri-n-butyltin chloride (TBTC) cause thymus atrophy in rodents. At low doses, antiproliferative modes of action have been shown to be involved, whereas at higher doses apoptosis seems to be the mechanism of thymotoxicity by these chemicals. In vitro, a similar concentration-dependency has been observed. The purpose of the present research was to investigate the mechanisms underlying DNA fragmentation induced by these organotin compounds in freshly isolated rat thymocytes. As previously shown for TBTC, DBTC is also able to significantly increase intracellular Ca2+ level ([Ca2+]i). The rise in [Ca2+]i, already evident 5 min after treatment, was followed by a dose- and time-dependent generation of reactive oxygen species (ROS) at the mitochondrial level. Simultaneously, organotins induced the release of cytochrome c from the mitochondrial membrane into the cytosol. ROS production and the release of cytochrome c were reduced by BAPTA, an intracellular Ca2+ chelator, or rotenone, an inhibitor of the electron entry from complex I to ubiquinone, indicating the important role of Ca2+ and mitochondria during these early intracellular events. Furthermore, we demonstrated that rotenone prevents apoptosis induced by 3 μM DBTC or TBTC and, in addition, that both BAPTA and Z-DEVD FMK (mainly a caspase-3 inhibitor) decreased apoptosis by DBTC (already shown for TBTC). Taken together these data show the apoptotic pathway followed by organotin compounds starts with an increase of [Ca2+]i, then continues with release of ROS and cytochrome c from mitochondria, activation of caspases, and finally results in DNA fragmentation.

Organotin-Induced Apoptosis as Observed in VitroIs Not Relevant for Induction of Thymus Atrophy at Antiproliferative Doses

The organotin compounds di- n-butyltin dichloride (DBTC) and tri- n-butyltin chloride (TBTC) selectively cause thymus atrophy. Previously, DBTC and TBTC were shown to inhibit proliferation of immature thymocytes, but other studies demonstrated that TBTC but not DBTC increased apoptosis in vitroand also in vivo.In this study, we examined whether apoptosis is increased in vitroby DBTC and TBTC at various concentrations and periods of incubation and whether apoptosis is involved in the induction of thymus atrophy at selective antiproliferative doses. In vitro,DBTC or TBTC at a concentration of 3 μ msignificantly increased DNA fragmentation in freshly isolated rat thymocytes after preincubation for 10 min followed by a 22-hr culture period. After continuous exposure for 22 hr, apoptosis was observed to be optimum at 1 μ mTBTC and 0.3 μ mDBTC and lower or absent at higher concentrations. Apparently, apoptosis induced by organotins in vitrodepends on both duration and concentration of exposure. Selective antiproliferative doses of DBTC nor TBTC increased apoptosis on day 1 or 2 after single oral exposure. In contrast, the corticosteroid dexamethasone caused a depletion of both small and large thymocytes and a marked increase of apoptosis on both days 1 and 2 after dosing. Thus, although apoptosis is involved in the in vitrocytotoxic effects of both organotin compounds, it seems not involved in thymus atrophy at a dose that selectively inhibits immature thymocyte proliferation.

Collection and Analysis of Butyltin Compounds in Air at Nanogram-Per-Cubic-Meter Levels

An analytical method for determining butyltin chlorides in air at low nanogram-per-cubic-meter levels was developed. Butyltin chlorides investigated were mono-n-butyltin trichloride (MBTC), di-n-butyltin dichloride (DBTC), and tri-n-butyltin chloride (TBTC). These tin chlorides were trapped on cartridges packed with Porapak-N, eluted with methylene chloride containing 0.3% HCl, hydridized with sodium borohydride, and analyzed by capillary gas chromatography with flame photometric detection. On the basis of a 20 m3 sample, a detection limit of 0.05 ng/m3 can be achieved.

Dysmorphogenic effects of di- n-butyltin dichloride in cultured rat embryos

Dysmorphogenic effects of di- n-butyltin dichloride (DBTC) were evaluated in vitro using the rat whole embryo culture system. Wistar rat embryos were explanted on day 8 of gestation and cultured for 68 hr. DBTC was added to the culture medium at the start of culture to achieve final concentrations of 3, 10 and 30 ng/ml. At the end of culture, the embryos were examined for vascularization development in the body and yolk sac, yolk sac diameter, crown-rump length, number of somite pairs, morphological score and external anomalies. Significantly and markedly decreased incidences of embryos with well developed vascularization in the body and yolk sac, yolk sac diameter, crown-rump length and number of somite pairs were found at 30 ng/ml. A concentration-dependent decrease in the morphological score and increase in the incidence of embryos with anomalies were noted, and the differences were significant for embryos exposed to 10 and 30 ng/ml DBTC. Open anterior neuropore and craniofacial abnormality were predominantly observed. It is concluded that DBTC possesses dysmorphogenic effects on postimplantation embryos in vitro.

The SCID-hu mouse as a tool in immunotoxicological risk assessment: effects of 2-acetyl-4(5)-tetrahydroxybutyl-imidazole (THI) and di- n-butyltin dichloride (DBTC) on the human thymus in SCID-hu mice

SCID mice engrafted with human fetal thymus and liver tissue fragments (SCID-hu mice) are currently considered as a new tool in human immunotoxicological risk assessment. Testing of various immunotoxicants exerting thymotoxicity via different intrathymic target cell types is necessary for validation of this model. Therefore, SCID-hu mice were exposed to 2-acetyl-4(5)-(1,2,3,4-tetrahydroxybutyl)-imidazole (THI), the immunotoxic component in the food additive, Caramel Colour III, or the organotin compound, di- n-butyltin dichloride (DBTC). Histopathological examination of the human thymus grafts of SCID-hu mice either exposed to THI or to DBTC showed a reduction in the relative size of the thymus cortex, an effect also described in rodents. These results indicate that the human thymus is a target for the immunotoxic action of both THI and DBTC. In addition, they indicate the promising potential of the SCID-hu mouse model as a tool for human immunotoxicological risk assessment.

The thymus atrophy-inducing organotin compound dbtc inhibits the binding of thymocytes to thymic epithelial cells

In this study, it is examined whether the organotin compound di-n-butyltindichloride (DBTC), which has been shown to inhibit immature thymocyte proliferation, is able to disturb the binding between thymocytes and thymic epithelial cells (TEC). To that end, an enzyme-linked binding assay was developed in which the amount of binding of Thy-1 + (mAb ER4)-thymocytes to the rat-derived TEC-line IT45R1 (IT45R1-TEC) could be detected. It was found that preincubation of thymocytes with 3–5 μM DBTC for 30 min inhibited the binding by 50–60% during a 1 h adhesion period. By extending the preincubation period to 1 h and the adhesion period to 22 h, 0.1 μM DBTC was already sufficient to reduce the binding with 60–80%. Further characterization of the binding revealed that splenic lymphocytes were unable to bind to the MHC class II-negative IT45R1-TEC. Since dextran sulfate inhibited the binding as well, sulfated polysaccharide-binding molecules such as Thy-I and CD2 are likely to be involved in the binding. Electron microscopy showed filament-containing microvilli at the site of interaction. The results are discussed in relation to the mechanism of DBTC-induced thymus atrophy.

Cellular and molecular aspects of organotin-induced thymus atrophy.

1. Organotin compounds, di-n-butyltin dichloride (DBTC) in particular, have been shown to cause thymus atrophy in the rat. 2. DBTC-induced thymus atrophy results from a depletion of small CD4+CD8+ thymocytes which is caused by a diminished production of immature CD4-CD8+ and CD4+CD8+ thymoblasts. 3. DBTC inhibits the activation, but not the differentiation of immature CD4-CD8+ thymocytes in vitro and in vivo suggesting a selective antiproliferative activity of DBTC. 4. DBTC inhibits the adhesion molecule-mediated binding of thymocytes to thymic epithelial cells. 5. DBTC enhances the Ca2+ release elicited by cross-linking of the T cell receptor complex (TcR alpha beta-CD3) on thymocytes and moreover delays cap formation of the TcR alpha beta-CD3 receptor. 6. It is concluded that DBTC possibly interferes with the functioning of the cytoskeleton. The relation of the in vitro findings to the inhibition of immature CD4-CD8+ thymocyte activation and the induction of thymus atrophy is unknown as yet.

The toxicity of bis(tri- n-butyltin)oxide (TBTO) and di- n-butyltindichloride (DBTC) in the small fish species Oryzias latipes (medaka) and Poecilia reticulata (guppy)

Toxicity studies were carried out on the Japanese medaka ( Oryzias latipes) with bis(tri- n-butyltin)oxide (TBTO) and di- n-butyltindichloride (DBTC), with emphasis on histopathological effects. Freshly fertilized eggs were exposed for 1 and 3 months to a concentration range of 0.1–32 μg TBTO/l in tank water. The range for DBTC was 320–3200 μg/l (1 month only). The histopathological effects included vacuolation of hepatocytes, tubulonephrosis and glomerulopathy, vacuolation of the retinal pigment epithelium, keratitis, hyperplasia and inflammation of oral and skin epithelium, hyperplasia and swelling of the gas gland epithelium and thyroid activation. No atrophy of the thymus was found. Except for the retinal and liver lesions, these changes occurred predominantly in the highest concentration with no essential differences in the lesions between 1 and 3 months, or between TBTO and DBTC exposure. Liver cell vacuolation was apparently caused by glycogen accumulation, as was confirmed in an additional experiment with guppies, a more expedient species. It is concluded that TBTO and DBTC have effects on the liver and gas gland, probably as a result of impaired glycogen breakdown. Effects on superficial epithelia are attributed to the irritative properties of these compounds. In addition, these compounds were toxic to kidney and retina. No-observed-effect concentrations using histopathology were 0.32 μg/l for TBTO, and lower than 320 μg/l for DBTC. Total tin and butyltins were determined by molecular absorption spectrometry, and gas chromatography with flame photometry, respectively, in guppies exposed to TBTO and DBTC. Considerable amounts of TBT were measured in DBTC-exposed fish, and chemical analysis indicated that DBTC contained TBT at a level that may account for the observed toxicity of DBTC.

An immunohistochemical study of dibutyltin-induced thymus atrophy.

Di-n-butyltin dichloride (DBTC) has been shown to be immunotoxic to rats. After feeding DBTC for several weeks, thymus and spleen weights were markedly reduced. As a consequence T cell-dependent immune responses were suppressed (Seinen et al 1979). Thymus atrophy seems to be caused by a direct action of the tin compound since it was not stress-mediated (Penninks et al 1985) and the number and viability of bone marrow cells were not affected (Seinen et al 1979). A single oral dose of DBTC also caused a marked reduction of thymus weights, which was maximal 4 days after dosing. Histologically, thymus weight reduction was associated with a severe loss of cortical thymus lymphocytes. Initially, DBTC diminished the number of large thymocytes in the first 2 days after exposure. Subsequently, the intermediate and small cells decreased in number at day 3 and 4 after exposure. It was concluded from these findings that DBTC-induced thymus atrophy is caused by reduction in the number of large thymic lymphocytes (Snoeij et al 1988 a). In this study, immunohistochemical methods are used to further characterize the DBTC-induced thymus atrophy.KeywordsSingle Oral DoseMajor Histocompatibility Complex AntigenThymus AtrophyThymus WeightMedullary AreaThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Dibutyltin and tributyltin compounds induce thymus atrophy in rats due to a selective action on thymic lymphoblasts

Di- n-butyltin dichloride (DBTC) or tri- n-butyltin chloride (TBTC) given in the diets of rats have previously been shown to cause atrophy of the thymus and subsequently suppression of the T-cell-dependent immune responses. To study the mechanism of the immunotoxic effects, the dose—effect relationships and the kinetics of the thymus atrophy caused by DBTC and TBTC were investigated in detail. A single oral dose of DBTC or TBTC to rats induced a dose-related reduction of relative thymus weight, which was maximal 4 days after intubation. The log dose—effect relationships for both compounds were linear and ran parallel over a dose range of 5–60 mg/kg. Dose levels calculated to cause 50% reduction of relative thymus weight were 18 mg DBTC and 29 mg TBTC per kg body wt. A single oral dose of mono- n-butyltin trichloride (MBTC), however, did not cause thymus atrophy at dose levels up to 180 mg/kg. The kinetics of the dibutyltin- and tributyltin-induced thymus atrophy in rats were investigated by measuring thymus weight, total thymic cell count, number of small, intermediate and large cells and the incorporation of DNA, RNA and protein precursors into isolated thymocytes during a period of 9 days after a single oral dose. DBTC and TBTC caused atrophy of the thymus due to a selective reduction in the number of rapidly proliferating lymphoblasts in the first 2 days after dosing. As a consequence the large pool of small lymphocytes declined in the following 2 days. On the fourth day, when atrophy was most pronounced, the frequency of the lymphoblasts increased above the controls. Within 9 days, all parameters were normal again. The kinetics of the thymus atrophy were generally the same for both compounds, but the effects caused by TBTC were less pronounced and somewhat delayed compared to DBTC. Considering the data from the present and previous studies, it is proposed that the thymus atrophy observed in rats orally exposed to tributyltin is caused by its metabolite dibutyltin.

Histopathological study of Poecilia reticulata (guppy) after long-term exposure to bis(tri- n-butyltin)oxide (TBTO) and di- n-butyltindichloride (DBTC)

The histopathologic effects in the small fish species Poecilia reticulata (guppy) were investigated after exposure to the biocide bis(tri- n-butyltin)oxide (TBTO), a contaminant of the aquatic environment. At the age of 3–4 wk animals were exposed to concentrations ranging from 0.01–32 μg TBTO/l over 1 and 3 months. In a comparative study young guppies were exposed to di- n-butyltindichloride (DBTC) for 1 month at a concentration range of 320–3200 μg/l. Both compounds induced thymus atrophy, hyperplasia of hemopoietic interstitial tissue of the kidney, and increase in number of free peritoneal cells in the body cavity, which were probably neutrophilic granulocyte analogs. In the liver vacuolation was increased, predominantly due to accumulation of fat and of glycogen; also muscle glycogen was increased. Effects of DBTC occurred at concentrations which were almost three orders of magnitude higher than of TBTO, and there were no indications that the TBTO-induced thymus atrophy is caused by the DBT-metabolite. In addition, at the higher concentrations of TBTO epidermal hyperplasia and keratitis occurred, as well as changes in the rods and cones layer of the retina. The ‘no-observed-effect’ concentration of TBTO was 0.01 μg/l, based on thymus atrophy, liver vacuolation or hyperplasia of the hemopoietic tissue, and this was 30-fold lower than when based upon classical toxicological criteria (growth). In the DBTC study, thymus atrophy was still present in the lowest concentration tested (320 μg/l) whereas the NOEC for mortality and behavior was 1800 μg/l. Atrrophy of the thymus, keratitis and skin irritation seem to be similar effects as found in mammals. It is concluded that long-term low dose TBTO-exposure of guppies causes thymus atrophy, increase in granulocytes, accumulation of glycogen and fat in the liver, and changes in cornea, retina and skin; except for the changes in the eye and skin, similar effects were induced by DBTC, although at manyfold higher concentrations.

Meso-2,3-dimercaptosuccinic acid increases the inhibition of glutathione S-transferase activity from rat liver cytosol supernatants by di-n-butyltin dichloride.

Di-n-butyltin dichloride (DBTC) and tricyclohexyltin chloride (TCHTC) inhibited the glutathione S-transferase activity of rat liver cytosolic supernatants towards 1-chloro-2,4-dinitrobenzene. Meso-2,3-dimercaptosuccinic acid increased inhibition of glutathione S-transferase by DBTC but lowered inhibition of the enzyme by TCHTC.

Di- n-butyltindichloride uncouples oxidative phosphorylation in rat liver mitochondria

In this study di- n-butyltindichloride (DBTC) was found to inhibit α-ketoacid-stimulated response of rat liver mitochondria to the addition of ADP and the uncoupler carbonyl cyanide p-trifluoromethoxyphenyl hydrazone (FCCP). The α-ketoglutarate oxidation was already inhibited at a level of 0.8 nmol DBTC/mg protein. When succinate was used as substrate together with rotenone, the State 3 and FCCP stimulated oxidation were not inhibited by DBTC. But from a level of 8.3 nmol DBTC/mg protein, the State 4 respiration was increased. It is concluded that in low amounts DBTC specifically blocks α-ketoacid dehydrogenases, but higher concentrations of this compound uncouples oxidative phosphorylation. However, this uncoupling will be masked when the NADH production from substrate oxidation is decreased by DBTC as will be in case of α-ketoacids.

Comparative toxicity of alkyltin and estertin stabilizers

In a 2-wk feeding study the oral toxicities of the estertin compounds bis-( β-carbobutoxyethyl)-tin dichloride (CBETC) and bis-( β-carbomethoxyethyl)tin dichloride (CMETC) and their hydrolysis products bis-( β-carboxyethyl)tin dichloride (CETC) were compared with those of the dialkyltin compounds di- n-octyltin dichloride (DOTC) and di- n-butyltin dichloride (DBTC) At a dietary level of 450 ppm the estertins did not affect weights, but at the relatively high level of 1350 ppm both caused growth retardation and a statistically significant decrease in the relative weight of the liver, while CBETC also reduced the relative weights of the thymus and spleen. A diminished amount of liver glycogen was the only treatment-related histopathological change observed in these organs. CETC caused no signs of toxicity up to a level of 1350 ppm. Slightly decreased body-weight gains were recorded in rats fed 50 ppm DBTC or 150 ppm DBTC or DOTC. but the main effect in dialkyltinfed rats was a decrease in lymphoid-organ weights. In rats fed 150 ppm DBTC or DOTC for 2 wk. the relative thymus weight was decreased by more than 70% compared with the control value and there was lymphocyte depletion in the thymus, especially the thymic cortex, and in thymus-dependent lymphoid areas of the spleen. Parenteral exposure demonstrated a similar difference in toxicity between these groups; a single ip or iv injection of 2.5 mg DBTC/kg body weight caused a slight reduction in bodyweight gain and severe thymic atrophy, whereas CBETC and CETC had no such effects even at 10 mg/kg. However, in vitro the activities of the estertins were similar to those of the dialkyltins. In lymphocyte metabolism studies, all these compounds induced a dose-dependent stimulation of glucose consumption, with maximum stimulation occurring at a level of 5 μ m with DBTC and CBETC and at 120 μ m with DOTC and CMETC. At higher exposure levels, glucose consumption fell sharply, oxygen consumption was reduced and lymphocyte viability was impaired. Since the dicarboxyltin compound CETC induced no signs of lymphocytotoxicity in the in vitro cell-metabolism, cell-viability or blast-transformation studies, hydrolysis of CBETC and CMETC to CETC in the rat is suggested as a possible explanation for the discrepancy between the lymphocytotoxic activity of the estertin compounds in vitro and the absence of lymphoid atrophy following in vivo exposure, and for the finding that in the rat CMETC and CBETC are much less toxic than the dialkyltin compounds DBTC and DOTC, which induce lymphocytotoxicity both in vitro and in vivo.