Fate and the biochemical effects of 2,4,6-trinitrotoluene exposure to tiger salamanders (Ambystoma tigrinum)

Responses of Oral 2,4,6-Trinitrotoluene (TNT) Exposure to the Common Pigeon (Columba livia): A Phylogenic and Methodological Comparison

Considerable concentrations of the explosive, 2,4,6-trinitrotoluene (TNT) have been found in the soil at many installations where explosives have been used, manufactured, assembled, or destroyed. To evaluate risk to avian receptors, measures of exposure are compared with a threshold level of sublethal toxicity. To date, a single feeding study has evaluated the responses of oral TNT exposure to birds with equivocal results regarding sublethal effects. The present study followed a controlled dosing regime comprising four dose groups and a control (200, 120, 70, 20, and 0 mg TNT/kg body weight [bw]-day) in the common pigeon ( Columba livia) for 60 days. Overt signs of toxicity occurred with both sexes between 2 and 3 weeks of exposure. Signs included weight loss, neuromuscular effects (e.g., ataxia, tremors, etc.), and scant red feces (chromaturia). Emetic events following dosing were common and proportional to dose; however, attempts to quantify vomitus compound concentration suggests that birds were marginally successful at removing TNT following administration. Eight of 12 and 2 of 12 males and females died or were moribund in the 200 and 120 mg/kg-day groups, respectively. Changes in hematological parameters, liver, kidney, and ovary weights were related to treatment. Dose-related changes in plasma albumin and sodium concentrations were also observed. These results suggest that subchronic exposure to TNT can adversely affect the central nervous system and hematological parameters in birds. Chemical analysis of blood detected concentrations of the two primary reduction metabolites, but not parent compound, suggesting that toxicity may be due to the bioaccumulation of a toxic intermediate.

Soils contaminated with explosives: Environmental fate and evaluation of state-of-the-art remediation processes (IUPAC Technical Report)

An explosion occurs when a large amount of energy is suddenly released. This energy may come from an over-pressurized steam boiler, from the products of a chemical reaction involving explosive materials, or from a nuclear reaction that is uncontrolled. In order for an explosion to occur, there must be a local accumulation of energy at the site of the explosion, which is suddenly released. This release of energy can be dissipated as blast waves, propulsion of debris, or by the emission of thermal and ionizing radiation. Modern explosives or energetic materials are nitrogen-containing organic compounds with the potential for self-oxidation to small gaseous molecules (N2, H2O, and CO2). Explosives are classified as primary or secondary based on their susceptibility of initiation. Primary explosives are highly susceptible to initiation and are often used to ignite secondary explosives, such as TNT (2,4,6-trinitrotoluene), RDX (1,3,5-trinitroperhydro-1,3,5-triazine), HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocane), and tetryl (N-methyl-N-2,4,6-tetranitro-aniline).

Effects of chronic 2,4,6,-trinitrotoluene, 2,4-dinitrotoluene, and 2,6-dinitrotoluene exposure on developing bullfrog (Rana catesbeiana) tadpoles

Chronic aqueous exposures were conducted using bullfrog (Rana catesbeiana) tadpoles (8 d old) exposed to TNT (0-4 mg/L), 2,4-DNT (0-4 mg/L), and 2,6-DNT (0-8 mg/L) for 90 d. Survival of tadpoles examined using Cox proportional hazard models was reduced at all concentrations tested. Percent of abnormal swimming and other morphological abnormalities after sublethal exposure to TNT, 2,4-DNT, and 2,6-DNT at 2 mg/L were also evaluated. The effects of TNT, 2,4-DNT, and 2,6-DNT on wet body mass, snout vent length (SVL), and developmental stage of surviving tadpoles were examined. Only 2,4-DNT did not have a significant effect on body mass or SVL, but all three compounds tested had significant effects on survival. Long-term continuous exposure to these compounds at concentrations of 0.25 mg/L could lead to significant changes in growth and survival of larval amphibians.

Whole-body and body-part-specific bioconcentration of explosive compounds in sheepshead minnows

Sheepshead minnows (Cyprinodon variegatus) were exposed to radiolabeled isotopes of the explosives 2,4,6-trinitrotoluene (TNT), exahydro-1,3,5-trinitro-1,3,5-triazine (commonly known as RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (commonly known as HMX), yielding the bioconcentration factors (BCF) of 3.3, 0.7, and 0.1 L kg(-1), respectively. For TNT, the body residue of transformation product exceeded that of the parent compound by factors of 1, 8, and 16 for total aminonitrotoluenes, total extractable compounds, and total transformation products, respectively, with substantial bioaccumulation of both non-identified extractable and unextractable (i.e., tissue-bound), compounds. In comparison, the sum body residues of RDX and HMX transformation products were <4 times higher than for parent compounds. The concentrations of RDX and HMX and their transformation products were similar among liver, viscera (excluding liver), gills, and body remains (integument and muscles), while 46% of the TNT transformation products resided in the liver, and 64% of the parent compound was in the viscera.

Toxic effects of oral 2-amino-4,6-dinitrotoluene in the Western fence lizard (Sceloporus occidentalis)

The compound 2-amino-4,6-dinitrotoluene (2A-DNT) was evaluated under laboratory conditions in the Western fence lizard (Sceloporus occidentalis) to assess the potential for reptile toxicity. Oral LD(50) values were 1406 and 1867 mg/kg for male and female lizards, respectively. Based on responses from a 14-day subacute study, a 60-day subchronic experiment followed where lizards were orally dosed at 0, 5, 15, 20, 25, 30 mg/kg-d. At day 60, number of days and survivors, food consumption, and change in body weight were inversely related to dose. Signs of toxicity were characterized by anorexia and generalized cachexia. Significant adverse histopathology was observed in hepatic tissue at ≥ 15 mg/kg-d, consistent with hepatocellular transdifferentiation. Based on survival, loss of body weight, diminished food intake, changes in liver, kidney, and testes, and increased blood urea nitrogen, these data suggest a LOAEL of 15 mg/kg-d and a NOAEL of 5 mg/kg-d in S. occidentalis.

From raw materials to validated system: the construction of a genomic library and microarray to interpret systemic perturbations in Northern bobwhite

The limited availability of genomic tools and data for nonmodel species impedes computational and systems biology approaches in nonmodel organisms. Here we describe the development, functional annotation, and utilization of genomic tools for the avian wildlife species Northern bobwhite (Colinus virginianus) to determine the molecular impacts of exposure to 2,6-dinitrotoluene (2,6-DNT), a field contaminant of military concern. Massively parallel pyrosequencing of a normalized multitissue library of Northern bobwhite cDNAs yielded 71,384 unique transcripts that were annotated with gene ontology (GO), pathway information, and protein domain analysis. Comparative genome analyses with model organisms revealed functional homologies in 8,825 unique Northern bobwhite genes that are orthologous to 48% of Gallus gallus protein-coding genes. Pathway analysis and GO enrichment of genes differentially expressed in livers of birds exposed for 60 days (d) to 10 and 60 mg/kg/d 2,6-DNT revealed several impacts validated by RT-qPCR including: prostaglandin pathway-mediated inflammation, increased expression of a heme synthesis pathway in response to anemia, and a shift in energy metabolism toward protein catabolism via inhibition of control points for glucose and lipid metabolic pathways, PCK1 and PPARGC1, respectively. This research effort provides the first comprehensive annotated gene library for Northern bobwhite. Transcript expression analysis provided insights into the metabolic perturbations underlying several observed toxicological phenotypes in a 2,6-DNT exposure case study. Furthermore, the systemic impact of dinitrotoluenes on liver function appears conserved across species as PPAR signaling is similarly affected in fathead minnow liver tissue after exposure to 2,4-DNT.

Toxicity of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) in three vertebrate species

The explosive, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine or high-melting explosive (HMX), has been found in soils in areas used for testing and training by the military. Many of these areas contain habitat for valued wildlife species. In an effort to better understand the environmental consequences from exposure, a reptilian (western fence lizard [Sceloporus occidentalis]), an amphibian (red-backed salamander [Plethodon cinereus]), and a mammalian species (rabbit [Oryctolagus cuniculus]) were exposed to HMX under controlled laboratory conditions. Lizards and rabbits were exposed to HMX by way of corn oil through gavage, and salamanders were exposed to HMX in soil. Two deaths occurred from acute oral exposures to lizards to 5000 mg HMX/kg BW. Histological and gross pathologic assessment suggested gut impaction as a possible cause of death. Salamanders exposed to concentrations of HMX in soil < or = 1970 mg HMX/kg soil for 10 days did not show adverse effects. Rabbits, however, showed neurologic effects manifested as hyperkinetic events with convulsions at > 24 h after oral exposures. An LD(50) for rabbits was calculated as 93 mg/kg (95% confidence interval 76-117). A subacute 14-day testing regime found a lowest observed effect level of 10 mg/kg-d and a no observed adverse effect level of 5 mg/kg-d based on hyperkinesia and seizure incidence, although changes suggesting functional hepatic alterations were also found. These data suggest that physiologic differences between species, particularly in gastrointestinal structure and function, can affect the absorption of HMX and hence lead to marked differences in toxicity from exposure to the same compound.

Interactions of 2,4,6-trinitrotoluene (TNT) with xenobiotic biotransformation system in European eel Anguilla anguilla (Linnaeus, 1758)

The aim of the present study was to investigate the interaction of 2,4,6-trinitrotoluene (TNT) with liver biotransformation enzymes in European eel Anguilla anguilla (Linnaeus, 1758). Eels were exposed to 0.5, 1 and 2.5mg/l nominal concentrations of TNT for 6 and 24h. Modulation of CYP1A1, UDPGT and GST genes was investigated by real-time PCR. Total CYP450 content, NADPH cytochrome c reductase activity, CYP1A and CYP2B-like activities, such as EROD, MROD and BROD, as well as GST and UDPGT activities, were measured by biochemical assays. An in vitro study was performed on EROD in order to evaluate catalytic modulation by TNT. No modulation of the CYP1A1 gene or protein was observed in TNT-exposed eels. On the other hand, a significant decline of EROD and MROD activities was observed in vivo. An increase in NADPH cyt c reductase, and phase II enzymes (UDPGT and GST) were observed at both gene expression and activity levels. The overall results indicated that TNT is a potential competitive inhibitor of CYP1A activities. A TNT metabolic pathway involving NADPH cyt c reductase and phase II enzymes is also suggested.

Effects of 2,4,6-trinitrotoluene (TNT) on phase I and phase II biotransformation enzymes in European eel Anguilla anguilla (Linnaeus, 1758)

The aim of this study was to investigate effects of the explosive 2,4,6-trinitrotoluene (TNT) on liver drug metabolizing genes and enzymes in the European eel Anguilla anguilla as a model fish species. Eels were exposed in vivo for 6h and 24h to 0.5, 1 and 2.5mg/L nominal concentrations of TNT. Expression of CYP1A, glutathione-S-transferase (pi-class; GST) and uridine-diphosphate glucuronosyltransferase (1-family) (UDPGT) genes was investigated by RT-PCR, and 7-ethoxy- and 7-methoxyresorufin-O-dealkylases (EROD, MROD), NADPH cyt c reductase (NADPH red), UDPGT and GST enzyme activities were measured by biochemical assays. An in vitro study was also performed, measuring only EROD activity. TNT exposure produced no modulation of CYP1A transcript expression while a significant inhibition of EROD enzyme activity was observed and confirmed in vitro. UDPGT transcript increased dose-dependently only at 6h while the UDPGT activity tended to increase dose-dependently at 24h. GST gene expression increased after 24h and significant increases of GST activity were observed both at 6 and 24h only at the highest TNT concentration. An increase of NADPH red activity was observed at 24h. Our results seem to indicate an inhibitory effect of TNT on CYP1A-dependent catalytic activities and a possible involvement of phase II enzymes as well as NADPH red in TNT metabolism in eels.

First observations of histopathological effects of 2,4,6-trinitrotoluene (TNT) in gills of European eel Anguilla anguilla (Linnaeus, 1758): histopathological effects of 2,4,6-trinitrotoluene in gills of European eel

The aim of the present study was to investigate the effects on gill morphology of the explosive 2,4,6-trinitrotoluene (TNT) in a model fish, the European eel, Anguilla anguilla (Linnaeus, 1758) to assess potential detrimental effects in marine fish due to its presence in dumping areas. Juvenile specimens of A. anguilla were exposed in vivo for 6 and 24 h to 0.5, 1 and 2.5 mg/l nominal concentrations of TNT using dimethyl sulfoxide (0.1 per thousand) as solvent carrier. Histological analysis of gills indicated that TNT induced several structural lesions. After 6h of exposure at 0.5 and 1 mg/l TNT, oedema of some secondary lamellae was evident: this change at the highest dose of 2.5 mg/l led to epithelial lifting and detachment from the endothelium and rupture of the branchial membrane and vascular congestion. After 24 h at 0.5 mg/l, increased oedema in secondary lamellae, extensive epithelial detachment and vascular congestion and dilation of lamellar capillaries and pooling of blood at 1 mg/l were observed. At 2.5 mg/l, epithelial hyperplasia, fusion of adjacent lamellae, obliteration of interlamellar spaces by means of tight junctions were also observed. Moreover, chloride cells proliferated along secondary lamellae, and mucus hypersecretion was evident. The overall results clearly indicate that gills are sensitive targets of TNT.

Endosulfan acute toxicity in Bufo bufo gills: ultrastructural changes and nitric oxide synthase localization

Endosulfan is an organochlorine pesticide used in agriculture for a wide range of crops. Endosulfan concentrations of up to 0.7 mg/L can be found in ponds and streams near sprayed agricultural fields. We investigated the short-term toxicity of endosulfan in common toad (Bufo bufo) tadpoles after 24, 48, and 96 h of exposure. Acute toxicity was evaluated at nominal concentrations ranging from 0.01 to 0.6 mg/L: concentrations that could be found after the application of pesticide. Our results show that 0.43 mg/L of endosulfan caused 50% mortality (LC(50)). The effects of a sublethal endosulfan concentration (0.2mg/L) on gill apparatus morphology were evaluated by scanning and transmission electron microscopy. Immunohistochemical methods were also applied to detect the expression pattern of the inducible isoform of nitric oxide synthase (iNOS) in the gills using the confocal laser scanner microscope. Exposure to 0.2mg/L of endosulfan caused an apparent increase in mucus production, the occurrence of secretory vesicles and lamellar bodies, a widening of intercellular spaces and additionally there was evidence of an inflammatory response in the gill apparatus. The morphological alterations occurred after 24h and were more pronounced after 48 and 96 h of exposure. Altered morphology and increased mucus secretion indicate impaired gas exchange and osmoregulation in the gills. In addition, there was an increase of iNOS expression after 24 and 48 h which may reflect hypoxia and inflammation in the gill epithelium. Our results clearly indicate that short-term exposure to a sublethal concentration of endosulfan, near the high end of the environmental range, disrupts gill morphology and function in B. bufo tadpoles.

Toxicological responses of red-backed salamanders (Plethodon cinereus) to subchronic soil exposures of 2,4-dinitrotoluene

Dinitrotoluenes are used as propellants and in explosives by the military and as such have been found at relatively high concentrations in the soil. To determine whether concentrations of 2,4-dinitrotoluene (2,4-DNT) in soil are toxic to amphibians, 100 red-backed salamanders (Plethodon cinereus) were exposed to either 1500, 800, 200, 75 or 0mg 2,4-DNT/kg soil for 28 days and evaluated for indicators of toxicity. Concentrations of 2,4-DNT were less than targets and varied with time. Most salamanders exposed to concentrations exceeding 1050 mg/kg died or were moribund within the first week. Salamanders exposed to soil concentrations exceeding 345 mg/kg lost >6% of their body mass though no mortality occurred. Overt effects included a reduction in feed consumption and an increase in bucco-pharyngeal oscillations in salamanders. These results suggest that only high soil concentrations of 2,4-DNT have the potential to cause overtly toxic effects in terrestrial salamanders.

Morphofunctional evidence of changes in principal and mitochondria-rich cells in the epidermis of the frog Rana kl. esculenta living in a polluted habitat

The epidermis of vertebrates is the body's principal barrier against environment and its possible contaminants. The presence of keratins, as well as specific detoxifying molecules or enzyme activities, in the various epidermis layers is believed to be involved in providing protection from harmful environmental influences. Anuran integument is poorly hornified and thus permeable to some endogenous and exogenous compounds and thus serves as a good bioindicator of overall environmental conditions. In the present investigation, we studied the epidermis of Rana kl. esculenta adult specimens collected at two different rice fields, relatively unpolluted and heavily polluted, respectively. Environmental pollution was assayed by chemical analysis performed on both sediments and animals. We evaluated the structural aspects of the epidermis at both light and electron microscopy levels and the pattern of keratinization by immunohistochemistry. Furthermore, we studied the activities of some enzymes (acid and alkaline phosphatase, nitric oxide synthase-related nicotinamide adenine dinucleotide phosphate dehydrogenase, glucose-6-phosphate dehydrogenase, catalase, nonspecific esterases, and succinic dehydrogenase) involved mainly in membrane transport, xenobiotics, and oxidative metabolism. Compared with controls, in polluted animals we found the following results: (1) an increase in pollutant levels (i.e., cadmium, mercury, and lead); (2) less keratinized superficial cells in the epidermis; and (3) changes in most enzyme activities in keratinocytes and mitochondria-rich cells (particularly glucose-6-phosphate dehydrogenase and esterases, both important to counteract oxidative and toxic stress). Taken as a whole, the present data indicate the morphofunctional plasticity of the frog epidermis in response to environmental contamination.

The involvement of cytochrome P450 system in the fate of 2,4,6-trinitrotoluene (TNT) in European eel [Anguilla anguilla (Linnaeus, 1758)]

TNT (2,4,6-trinitrotoluene) was the most common nitro aromatic explosive available in World War II ammunitions. The presence of ordnance dumped at sea might represent a great concern for marine species living close to dumping sites and the toxicological properties of the chemicals released into the marine environments need to be evaluated. The aim of the present study is to investigate the involvement of CYP (cytochrome P450) system in the metabolism of TNT in marine organisms by using the European eel [Anguilla anguilla (Linnaeus, 1758)] as model species. In vivo exposure to sublethal concentration of TNT (0.5, 1 and 2.5 mg/l) leads to a significant decrease in the phase I CYP1A catalytic activities such as EROD (7-ethoxyresorufin-O-de-ethylase) and MROD (7-methoxyresorufin-O-de-ethylase). On the opposite, a significant increase in NADPH cytochrome c reductase activity as well as phase II UDP-glucuronosyltransferase activity is observed. An inhibition at enzyme level is hypothesized for both CYP1A enzymes, also confirmed by a similar decrease observed after in vitro exposure. An active role of NADPH cytochrome c reductase and phase II enzymes in the TNT metabolism may also be hypothesized.

Solid phase microextraction of aminodinitrotoluenes in tissue

Tubifex tubifex metabolizes 2,4,6-trinitrotoluene (TNT) to 2-amino-4,6-dinitrotoluene (2ADNT) and 4-amino-2,6-dinitrotoluene (4ADNT). Elimination rates of metabolically-generated ADNTs are low compared to ADNTs absorbed directly from water, suggesting that metabolically-generated ADNTs may be bound or sequestered within tissue and therefore less available for elimination. A solid phase microextraction (SPME) technique was used to extract ADNTs from T. tubifex tissue to investigate the recalcitrance of metabolically-generated ADNTs. As SPME is a gentle, non-depletive, equilibrium sampling technique useful for measuring "available" organic compounds, we hypothesized that metabolically-generated ADNTs would be less extractable than absorbed ADNTs. T. tubifex were exposed to two scenarios to generate tissues containing absorbed ADNTs and metabolically-generated ADNTs. Tissue was then homogenized in a neutral buffer solution. Polyacrylate-coated (PA) SPME fibers were deployed and agitated in tissue homogenates to measure available ADNTs. Extractability of ADNTs from tissue containing metabolically-generated ADNTs was significantly less than expected: 50-60% based on the theoretical fiber-water partition ratio. Extractability of absorbed ADNTs was significantly higher (81-90%), and not significantly different than expected. The lower SPME extractability of metabolically-generated ADNTs may stem from the unavailability of metabolically-generated ADNTs sequestered in tissue or bound to tissue macromolecules during metabolism of TNT to ADNT. Tissue extractions using SPMEs may be able to estimate bound organic residues in tissue and serve to indicate the toxicological bioavailability of tissue-associated organic compounds.

Phytotoxicity of nitroaromatic energetic compounds freshly amended or weathered and aged in sandy loam soil

The toxicities of 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitrobenzene (TNB), 2,4-dinitrotoluene (2,4-DNT), and 2,6-dinitrotoluene (2,6-DNT) to terrestrial plants alfalfa (Medicago sativa L.), Japanese millet (Echinochloa crusgalli L.), and perennial ryegrass (Lolium perenne L.) were determined in Sassafras sandy loam soil using seedling emergence, fresh shoot, and dry mass measurement endpoints. A 13-week weathering and aging of energetic materials in soils, which included wetting and drying cycles, and exposure to sunlight of individual soil treatments, was incorporated into the study design to better reflect the soil exposure conditions in the field than toxicity determinations in freshly amended soils. Definitive toxicity tests showed that dinitrotoluenes were more phytotoxic for all plant species in freshly amended treatments based on EC20 values for dry shoot ranging from 3 to 24mgkg(-1) compared with values for TNB or TNT ranging from 43 to 62mgkg(-1). Weathering and aging of energetic materials (EMs) in soil significantly decreased the toxicity of TNT, TNB or 2,6-DNT to Japanese millet or ryegrass based on seedling emergence, but significantly increased the toxicity of all four EMs to all three plant species based on shoot growth. Exposure of the three plant species to relatively low concentrations of the four compounds initially stimulated plant growth before the onset of inhibition at greater concentrations (hormesis).

Tentative biomarkers for 2,4,6-trinitrotoluene (TNT) in fish (Oncorhynchus mykiss)

2,4,6-Trinitrotoluene (TNT) is the major explosive in ammunition dumped into lakes and the sea after World War II. To identify useful biomarkers of TNT-exposure for forthcoming fish monitoring studies at ammunition dumping sites, rainbow trout (Oncorhynchus mykiss) were intraperitoneal (i.p.) injected with TNT in peanut oil at doses of 0, 100, 200 or 400 mg TNT/kg body weight and sampled 72 h later. The study covered blood parameters, and hepatic antioxidant and detoxifying enzymes. Fish treated with TNT had an increased glutathione S-transferase (GST) activity and glutathione reductase (GR) activity, and a decreased percentage of oxidised glutathione (%GSSG) compared to the control group. In addition to increased methemoglobin, the increased glutathione and glutathione dependent enzyme activities indicate that TNT oxidises macromolecules and activates antioxidant defence systems which may be useful as general biomarkers of TNT-exposure. The fish bile was analysed for TNT and its metabolites by gas chromatography-mass spectrometry (GC-MS), and the toxicity of the bile was determined with the cladoceran Ceriodaphnia dubia. A dose-dependent increase in TNT, 2-amino-4,6-dinitrotoluene (2-ADNT) and 4-amino-2,6-dinitrotoluene (4-ADNT) was found in the hydrolysed bile of the TNT-treated fish. These results indicate that the fish are able to detoxify and excrete TNT and suggest that the detection of TNT, 2-ADNT and 4-ADNT in bile may be suitable as a direct marker of exposure to TNT.

Effects of steroids and dioxin (2,3,7,8-TCDD) on the developing wolffian ducts of the tiger salamander (Ambystoma tigrinum)

This study was undertaken to investigate effects of the prototypical dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on steroid-dependent development of the wolffian ducts of an amphibian, the tiger salamander (Ambystoma tigrinum). Larvae with immature gonads and undeveloped mullerian ducts were injected with the steroid hormones estradiol (E2), dihydrotestosterone (DHT), or vehicle alone. Additionally, steroid-treated and vehicle-control larvae were immersed in sub-lethal solutions of technical grade TCDD (0, 0.0003, 0.003, 0.03, 0.3, and 3.0 microg TCDD/L). Both steroid treatments stimulated hypertrophy of the wolffian duct epithelium and an increase in mean epithelial cell size. Only DHT treatment stimulated epithelial cell proliferation. TCDD stimulated wolffian duct hypertrophy through an increase in mean epithelial cell size. TCDD acted as an androgen agonist on wolffian duct epithelial area and epithelial cell size. TCDD had no effect on wolffian duct epithelium among E2-injected animals. Stimulatory effects on cell size were observed at 0.0003 microg/L TCDD in saline-injected animals and at 0.003 microg/L TCDD in DHT-injected animals. Both E2 and DHT stimulated growth of the wolffian ducts early in development. Technical grade TCDD alone mimics E2 and DHT action but exhibits an androgen-agonistic action in the presence of exogenously administered DHT. Implications of possible interactions between TCDD and xenosteroids are discussed.

Biotransformation of 2,4,6-trinitrotoluene (TNT) by enchytraeids (Enchytraeus albidus) in vivo and in vitro

2,4,6-Trinitrotoluene (TNT) is toxic to soil invertebrates, but little is known about its toxicokinetic behavior in soil. Tissue residue analysis was used to evaluate whether the presence of TNT and its reduced metabolites in soil invertebrates was due to uptake of these compounds from the soil into the organism, or due to microbial transformation of TNT associated with the organism followed by uptake. Adult white potworms (Enchytraeus albidus) were exposed to non-lethal concentrations of TNT in amended artificial soil for 21 d, or to TNT in solution for 20 h. Soil exposure studies confirmed earlier reports that TNT was transformed in enchytraeids in vivo to 2- and 4-aminodinitrotoluenes. However, enchytraeid exposure to TNT in solution led to the additional presence of 2,4-diaminonitrotoluene as well as 2- and 4- hydroxyamino-dinitrotoluenes and azoxy-compounds, suggesting that TNT can be metabolized in vivo in the absence of soil. Incubation of unexposed enchytraeid homogenates with TNT led to a protein-dependent appearance of these metabolites in vitro after > or =16 h incubation. Cellular fractionation studies indicated that most of this activity resided in the 8000 x g pellet, and was completely inhibited by broad-spectrum antibiotics. These studies demonstrate that enchytraeids can transform TNT in vivo and in vitro, at least in part, by bacteria associated with the host organism.

Preliminary kinetics and metabolism of 2,4,6-trinitrotoluene and its reduced metabolites in an aquatic oligochaete

We examined the toxicokinetics and metabolism of 2,4,6-trinitirotoluene (TNT) and four of its major reduced metabolites (2-amino-4,6-dinitrotoluene (2ADNT), 4-amino-2,6-dinitrotoluene (4ADNT), and 2,4-diamino-6-nitrotoluene (2,4DANT)) in the freshwater, aquatic oligochaete Tubifex tubifex exposed to spiked, reconstituted water. In uptake experiments with each compound, steady state concentrations were reached within 1h, and all absorbed compounds were completely eliminated in 0-3 h. The appearance of 2ADNT and 4ADNT (from metabolism of absorbed TNT) was five times slower, reaching 95% of steady state in 14.2-16.1h. Approximately, 82% of absorbed TNT was metabolized to ADNTs; metabolism to 4ADNT was favored over 2ADNT by a factor of 3. No further metabolism of ADNTs to DANTs was detected. After a loss of 29-50% of metabolically-generated ADNTs during the first hour of the TNT depuration experiment, Tubifex ADNT concentrations remained constant throughout the 53h depuration period. This suggests differences between the toxicokinetics of absorbed ADNTs and the toxicokinetics of metabolically-generated ADNTs. Experiments using radiolabeled (14C) TNT revealed that only 15-47% of 14C-TNT equivalents were identified as TNT, 2ADNT, or 4ADNT, indicating significant metabolism and/or binding to biomolecules. Of unidentified 14C-TNT equivalents, 28-38% remained unextractable. Both unextractable and extractable unidentified substances increased throughout the 54 h 14C-TNT uptake experiment. The unidentified portions of the radiolabel were not eliminated during a 53-h depuration experiment. Bioconcentration factors (BCFs) for HPLC-detectable compounds were found to be linearly related to log K(OW) (r2 = 0.9963). BCFs for 2ADNT, 4ADNT, and 2,4DANT were 10.22, 12.41, and 2.75, respectively. The BCF for TNT was 12.25, based on a molar sum of total TNT and its metabolites (SigmaTNT + 2ADNT + 4ADNT), and 2.53 based on TNT only. Compound hydrophobicity predicted the toxicokinetics and bioconcentration of compounds absorbed from water, however, the large discrepancy between the toxicokinetics of absorbed versus metabolically-generated ADNTs and the bioconcentration and toxicokinetics of the unidentified substances warrant further investigation.

Toxicity and bioaccumulation of reduced TNT metabolites in the earthworm Eisenia andrei exposed to amended forest soil

Soils contaminated with 2,4,6-trinitrotoluene (TNT) and TNT primary reduction products have been found to be toxic to certain soil invertebrates, such as earthworms. The mechanism of toxicity of TNT and of its by-products is still not known. To ascertain if one of the TNT reduction products underlies TNT toxicity, we tested the toxicity and bioaccumulation of TNT reduction products. 2-Amino-4,6-dinitrotoluene (2-ADNT), 4-amino-2,6-dinitrotoluene (4-ADNT), 2,4-diamino-6-nitrotoluene (2,4-DANT) and 2,6-diamino-4-nitrotoluene (2,6-DANT) were tested separately in adult earthworms (Eisenia andrei) following a 14-d exposure to amended sandy loam forest soil. TNT, 4-ADNT, and 2-ADNT were lethal to earthworms (14-d LC(50) were: 580, 531 and 1088 micromol kg(-1), or 132, 105 and 215 mgkg(-1) dry soil, respectively) and gave the following order of toxicity: 4-ADNT>TNT>2-ADNT. Exposure to 2,4-DANT and to 2,6-DANT caused no mortality at 600 micromol kg(-1) or 100 mgkg(-1) dry soil. We found that all four TNT reduction products accumulated in earthworm tissues and 2-ADNT reached the highest levels at 3.0+/-0.3 micromol g(-1) tissue. The 14-d bioaccumulation factors were 5.1, 6.4, 5.1 and 3.2 for 2-ADNT, 4-ADNT, 2,4-DANT and 2,6-DANT, respectively. Results also suggest that some TNT metabolites are at least as toxic as TNT and should be considered when evaluating the overall toxicity of TNT-contaminated soil to earthworms.

Models of 2,4,6-trinitrotoluene (TNT) initial conversion by yeasts

The original models of the initial steps of 2,4,6-trinitrotoluene (TNT) conversion by yeasts are presented. Saccharomyces sp. ZS-A1 reduced nitro groups of TNT producing isomeric monohydroxylaminodinitrotoluenes (HADNT) as the key initial metabolites (molar ratio HADNT/TNT was up to 0.81), whereas aminodinitrotoluenes (ADNT) and the hydride-Meisenheimer complex of TNT (H-TNT) were the minor products. Conversely, Candida sp. AN-L13 transformed TNT almost quantitatively into H-TNT, thus realizing the alternative attack, consisting of the TNT aromatic ring reduction. The third type of conversion, revealed in Candida sp. AN-L14, is the combination of both above mechanisms and produces an equimolar mix of HADNT and H-TNT. In the toxicity tests with Paramecium caudatum, the supernatant of Saccharomyces sp. ZS-A1, which converts TNT into HADNT, was most toxic while the supernatant of Candida sp. AN-L13 (TNT --> H-TNT) was least toxic. The microorganisms converting TNT quantitatively to the reactive metabolites can be useful for their immobilization through the detoxifying interaction with the soil components such as humic compounds.