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PubMed1999

Refined crystal structures of reaction centres from Rhodopseudomonas viridis in complexes with the herbicide atrazine and two chiral atrazine derivatives also lead to a new model of the bound carotenoid.

In a reaction of central importance to the energetics of photosynthetic bacteria, light-induced electron transfer in the reaction centre (RC) is coupled with the uptake of protons from the cytoplasm at the binding site of the secondary quinone (QB). It has been established by X-ray crystallography that the triazine herbicide terbutryn binds to the QB site. However, the exact description of protein-triazine interactions has had to await the refinement of higher-resolution structures. In addition, there is also interest in the role of chirality in the activity of herbicides. Here, we report the structural characterisation of triazine binding by crystallographic refinement of complexes of the RC either with the triazine inhibitor atrazine (Protein Data Bank (PDB) entry 5PRC) or with the chiral atrazine derivatives, DG-420314 (S(-) enantiomer, PDB entry 6PRC) or DG-420315 (R(+) enantiomer, PDB entry 7PRC). Due to the high quality of the data collected, it has been possible to describe the exact nature of triazine binding and its effect on the structure of the protein at high-resolution limits of 2.35 A (5PRC), 2.30 A (6PRC), and 2.65 A (7PRC), respectively. In addition to two previously implied hydrogen bonds, a third hydrogen bond, binding the distal side of the inhibitors to the protein, and four additional hydrogen bonds mediated by two tightly bound water molecules on the proximal side of the inhibitors, are apparent. Based on the high quality data collected on the RC complexes of the two chiral atrazine derivatives, unequivocal assignment of the structure at the chiral centres was possible, even though the differences in structures of the substituents are small. The structures provide explanations for the relative binding affinities of the two chiral compounds. Although it was not an explicit goal of this work, the new data were of sufficient quality to improve the original model also regarding the structure of the bound carotenoid 1,2-dihydroneurosporene. A carotenoid model with a cis double bond at the 15,15' position fits the electron density better than the original model with a 13,14-cis double bond.

Atrazine↗
PubMed1993

A comparative study of effects of atrazine on xenobiotic metabolizing enzymes in fish and insect, and of the in vitro phase II atrazine metabolism in some fish, insects, mammals and one plant species.

1. Atrazine (3 daily i.p. doses of 0.20 mg/kg or 10 ppb in the water for 14 days) did not change the xenobiotic metabolizing enzyme activities (XME) towards the substrates aldrin epoxidase (AE), NADPH-cytochrome c reductase (NCCR), 7-ethoxyresorufin O-deethylase (EROD), 1-chloro-2,4-dinitro-benzene (CDNB) and 1,2-dichloro-4-nitrobenzene (DCNB) in trout liver (Oncorhynchus mykiss) compared to the controls. 2. Various treatment regimens of atrazine in a semisynthetic diet changed the XME activities towards AE, NCCR, CDNB and DCNB in the cabbage moth (Mamestra brassica L.) soft tissues and midgut compared to the controls. 3. A life-long cabbage diet induced the XME activity towards CDNB in the cabbage moth soft tissues and midgut, whereas no differences in the activities towards AE, NCCR and DCNB were observed compared to controls on a semi-synthetic diet. 4. The cabbage moth GSTs bound poorly to a glutathione (GSH)-linked epoxy-activated Sepharose 6-B; however, based on the CDNB activity recovered by a GSH elution, there were no differences in the molecular weights of the partly purified subunits (27, 26 and 25 kDa) or the pIs (5.4, 4.8, and 4.1) of the molecules in the soft tissues or midguts from respectively atrazine treated and control cabbage moth.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2006

Mixed-effect models for evaluating multiple measures of atrazine exposure among custom applicators.

The exposure of custom (or commercial) applicators to the herbicide atrazine was measured in environmental (hand wash and dermal patch) and biological (urine and saliva) samples. Surrogate exposure data, such as amount of atrazine sprayed, were also collected. A systematic sampling design was used that included both spray and nonspray days. Fifteen applicators were sampled 5 to 7 days each during a 6-week spring spray season for a total of 89 sampled days. Mixed-effect regression modeling was used to examine the relationship among the surrogate, environmental, and biological atrazine exposure measures. Surrogate measures of atrazine application (either kg of atrazine sprayed or spray atrazine [yes/no]) were significantly associated with increased levels of atrazine or atrazine equivalents (eq) in hand wash, thigh patch, 4-6 p.m. saliva, and 24-hour urine samples. Two days of spraying information (day of sampling and day before sampling) were needed to optimally estimate atrazine biomarkers in the biological samples, whereas only 1 day of spraying information (day of sampling) was needed to estimate atrazine levels in the environmental samples. Thigh and hand atrazine exposures were significantly associated with increased atrazine and atrazine eq. levels in the 4-6 p.m. saliva and 24-hour urine samples, respectively. Levels of 4-6 p.m. salivary atrazine were also significantly associated with increased levels of 24-hour urinary atrazine eq. Atrazine levels in the 4-6 p.m. saliva samples tracked most closely with evening and next morning urinary atrazine eq. Number of days into the study at the time of sample collection predicted urinary and salivary atrazine levels independent of other fixed effects. These results indicate that either surrogate, environmental, or biological exposure measures can be used in appropriately specified models to estimate urinary and salivary atrazine biomarker levels.

Air Pollutants, Occupational↗
PubMed1996

Biodegradation of atrazine in surface soils and subsurface sediments collected from an agricultural research farm.

The purpose of the present study was to assess atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) mineralization by indigenous microbial communities and to investigate constraints associated with atrazine biodegradation in environmental samples collected from surface soil and subsurface zones at an agricultural site in Ohio. Atrazine mineralization in soil and sediment samples was monitored as 14CO2 evolution in biometers which were amended with 14C-labeled atrazine. Variables of interest were the position of the label ([U-14C-ring]-atrazine and [2-14C-ethyl]-atrazine), incubation temperature (25 degrees C and 10 degrees C), inoculation with a previously characterized atrazine-mineralizing bacterial isolate (M91-3), and the effect of sterilization prior to inoculation. In uninoculated biometers, mineralization rate constants declined with increasing sample depth. First-order mineralization rate constants were somewhat lower for [2-14C-ethyl]-atrazine when compared to those of [U-14C-ring]-atrazine. Moreover, the total amount of 14CO2 released was less with [2-14C-ethyl]-atrazine. Mineralization at 10 degrees C was slow and linear. In inoculated biometers, less 14CO2 was released in [2-14C-ethyl]-atrazine experiments as compared with [U-14C-ring]-atrazine probably as a result of assimilatory incorporation of 14C into biomass. The mineralization rate constants (k) and overall extents of mineralization (Pmax) were higher in biometers that were not sterilized prior to inoculation, suggesting that the native microbial populations in the sediments were contributing to the overall release of 14CO2 from [U-14C-ring]-atrazine and [2-14C-ethyl]-atrazine. A positive correlation between k and aqueous phase atrazine concentrations (Ceq) in the biometers was observed at 25 degrees C, suggesting that sorption of atrazine influenced mineralization rates. The sorption effect on atrazine mineralization was greatly diminished at 10 degrees C. It was concluded that sorption can limit biodegradation rates of weakly-sorbing solutes at high solid-to-solution ratios and at ambient surface temperatures if an active degrading population is present. Under vadose zone and subsurface aquifer conditions, however, low temperatures and the lack of degrading organisms are likely to be primary factors limiting the biodegradation of atrazine.

Adsorption↗
PubMed2006

Determination of atrazine and its metabolites in mouse urine and plasma by LC-MS analysis.

Atrazine is a herbicide widely used on agricultural commodities. Existing analytical methods to analyze atrazine and its metabolites in biological matrices have various drawbacks. Thus, further development of such methods will be needed to correlate the growing number of toxicological effects associated with atrazine exposure with the concentrations of this compound and its metabolites in plasma, urine, and tissues. The purpose of this study was to develop a broad and sensitive LC-MS method for the analysis of atrazine and its metabolites in mouse urine and plasma. We were able to simultaneously measure atrazine and its major mammalian metabolites, which include didealkyl atrazine, desisopropyl atrazine, desethyl atrazine, atrazine-glutathione conjugate, and atrazine-mercapturate, using preparation procedures that used small sample volumes of plasma and urine (0.25 and 0.5 ml, respectively). Furthermore, derivatization of analytes prior to analysis was unnecessary. This method was used to analyze plasma and urine samples following single in vivo oral exposures of a limited number of mice to atrazine (doses, 5-250 mg/kg body weight) to demonstrate the utility of this LC-MS method. The data obtained from this study suggest that atrazine is rapidly metabolized in mice. Didealkyl atrazine was the most abundant metabolite detected in the urine and plasma samples (approximately 1000 microM in 24-h urine and approximately 100 microM in plasma following the highest dose of atrazine), with lesser quantities of mono N-dealkylated metabolites and thio conjugates of atrazine observed. We also used this methodology in a preliminary study of cytochrome P450-catalyzed metabolism of atrazine in vitro. The results obtained in this study suggest that this method will be a useful tool for the determination of atrazine and its metabolites in future pharmacokinetic studies and for the subsequent development and refinement of biologically based models of atrazine disposition.

Animals↗
PubMed2006

2004 National Atrazine Occurrence Monitoring Program using the Abraxis ELISA method.

The goal of this project was to gain a better understanding of atrazine occurrence in the United States by surveying drinking water utilities' sources and finished water for atrazine on a weekly basis for seven months. Atrazine is a contaminant of interest because the United States Environmental Protection Agency (USEPA) has found short-term atrazine exposure above the drinking water maximum contaminant level (MCL) to potentially cause heart, lung, and kidney congestion, low blood pressure, muscle spasms, weight loss, and damage to the adrenal glands. Long-term exposure to atrazine concentrations above the drinking water MCL has been linked to weight loss, cardiovascular damage, retinal and muscle degeneration, and cancer. This survey effort improved upon previously conducted atrazine surveys through intensive, high frequency sampling (participating plants sampled their raw and finished water on a weekly basis for approximately seven months). Such an intensive effort allowed the authors to gain a better understanding of short-term atrazine occurrence and its variability in drinking water sources. This information can benefit the drinking water industry by facilitating (1) better atrazine occurrence management (i.e., awareness when plants may be more susceptible to atrazine), (2) more efficient atrazine control (e.g., effective treatment alternatives and more effective response to atrazine occurrence), and (3) treatment cost reduction (e.g., efficient atrazine control can result in substantial cost savings). Forty-seven drinking watertreatment plants located primarily in the Midwestern United States participated in the survey and sampled their raw and finished water on a weekly basis from March through October. Samples were analyzed using the Abraxis enzyme-linked immunosorbent assay (ELISA) test kit. Confirmation samples for quality assurance/quality control (QA/QC) purposes were analyzed using solid-phase extraction (SPE) followed by gas chromatography mass spectrophotometry (GC/MS). Several important conclusions can be drawn from this study including (1) surface waters were confirmed to be more vulnerable to atrazine contamination than groundwater sources, (2) peak atrazine concentrations corresponded well to precipitation/runoff events, and (3) atrazine occurrence tended to be uniform geographically when compared by river drainage basins. In addition, this project confirmed that the Abraxis atrazine ELISA test kit tended to have a positive bias (i.e., the measured ELISA concentration was higher than the actual concentration) in most measured samples. Finished samples tended to have more of a positive bias than raw water samples. Therefore, this bias may limit the effectiveness for ELISA for regulatory monitoring. There are many other applications for ELISA, however, including frequent monitoring for early detections of atrazine concentration changes that might trigger conventional analysis by GC/MS or be used for activated carbon dosing or other treatment operating controls.

Atrazine↗
PubMed2000

Saliva biomonitoring of atrazine exposure among herbicide applicators.

A field study was conducted in which saliva samples were collected from a cohort of herbicide applicators during the pre-emergent spray season in Ohio in 1996. Atrazine concentrations were detected in human saliva samples using an enzyme-linked immunosorbent assay (ELISA) method. Trend due to atrazine exposure and subsequent elimination in the body were evidenced by the temporal pattern of decreasing atrazine concentrations in saliva over time. Median salivary concentrations of atrazine on non-spray days were significantly lower than on spray days for each sampling time (Mann-Whitney U-Wilcoxon rank sum test, P < 0.01). Within spray days, median salivary atrazine concentrations were significantly higher on days atrazine was sprayed than on days herbicides other than atrazine were sprayed for each sampling time (Mann-Whitney U-Wilcoxon rank sum test, P = 0.02 for 4 6 p.m. samples, P = 0.04 for bedtime samples, P = 0.03 for next-morning samples). Median salivary atrazine concentrations on days atrazine was sprayed were higher than the median concentration for the corresponding sampling time on non-spray days and on days when other herbicides were sprayed. Salivary concentration of atrazine is a plausible indicator of those days in which atrazine spraying was likely to have occurred. Salivary concentrations of atrazine not only reflect exposures resulting from spraying atrazine, but also exposures from other field activities where applicators may come in contact with atrazine. The results of this study confirmed data from animal experiments that atrazine is able to cross the cell membranes of salivary glands, and can be measured in human saliva with high sensitivity. The sampling method itself is convenient and easy to use in the field, with a high compliance rate, and analytical procedures are rapid and inexpensive. It is, therefore, concluded that saliva sampling of atrazine exposure among herbicide applicators is a feasible biomonitoring method.

Adult↗
PubMedDate not supplied

Atrazine effects on testosterone levels and androgen-dependent reproductive organs in peripubertal male rats.

Previous studies have reported that atrazine, a widely used herbicide that selectively inhibits photosynthesis in broadleaf and grassy weeds, has adverse effects on reproductive function in the male, suggesting a direct effect of atrazine on the hypothalamicpituitary-testicular axis. As yet, however, no studies have critically examined the doses of atrazine that elicit such effects, and few have focused on the mechanism by which atrazine acts. Herein we report a dose-response study of the effects of atrazine ingestion on reproductive function in male Sprague-Dawley rats during a critical developmental period, the peripubertal period. Atrazine was administered by gavage to rats from day 22 to day 47 of age, at doses of 1-200 mg/kg body weight per day. Atrazine administration of up to 50 mg/kg per day had no effect on any of the measured variables. Serum testosterone concentration was reduced by atrazine at doses of 100 and 200 mg/kg per day, as were seminal vesicle and ventral prostate weights. Intratesticular testosterone concentration was reduced in parallel with serum testosterone, suggesting that the reductions in serum testosterone resulted from reduced testosterone production by Leydig cells or from changes in testosterone metabolism within the testis, or both. Serum luteinizing hormone (LH) concentration was reduced despite the reduced serum testosterone, suggesting an effect on the hypothalamus, the pituitary gland, or both. At the termination of the study, the average body weight of rats receiving atrazine at 100 mg/kg per day was found to be reduced by approximately 9%. This suggested the possibility that the effects of atrazine on the reproductive tract may not be direct, but rather, the noted deficits of the male reproductive tract resulted from reduced food intake by the treated rats. We tested this by feeding control (vehicle-gavaged) rats amounts of food equivalent to that consumed by the atrazine-fed rats, and then assessing reproductive tract endpoints. Even mild food restriction resulted in reductions in serum testosterone concentration, in the weights of androgen-dependent organs, and in serum LH concentration; the same deficits that were seen in atrazine-gavaged rats. Indeed, the effects of atrazine on the male reproductive tract seen in rats receiving atrazine at greater than 50 mg/kg per day could not be distinguished from the effects of reduced food consumption. These results suggest that caution must be exercised before concluding that atrazine (or any potentially toxic chemical) has direct, detrimental effects.

Age Factors↗
PubMed1991

Atrazine Resistance in a Velvetleaf (Abutilon theophrasti) Biotype Due to Enhanced Glutathione S-Transferase Activity.

We previously reported that a velvetleaf (Abutilon theophrasti Medic) biotype found in Maryland was resistant to atrazine because of an enhanced capacity to detoxify the herbicide via glutathione conjugation (JW Gronwald, Andersen RN, Yee C [1989] Pestic Biochem Physiol 34: 149-163). The biochemical basis for the enhanced atrazine conjugation capacity in this biotype was examined. Glutathione levels and glutathione S-transferase activity were determined in extracts from the atrazine-resistant biotype and an atrazine-susceptible or "wild-type" velvetleaf biotype. In both biotypes, the highest concentration of glutathione (approximately 500 nanomoles per gram fresh weight) was found in leaf tissue. However, no significant differences were found in glutathione levels in roots, stems, or leaves of either biotype. In both biotypes, the highest concentration of glutathione S-transferase activity measured with 1-chloro-2,4-dinitrobenzene or atrazine as substrate was in leaf tissue. Glutathione S-transferase measured with 1-chloro-2,4-dinitrobenzene as substrate was 40 and 25% greater in leaf and stem tissue, respectively, of the susceptible biotype compared to the resistant biotype. In contrast, glutathione S-transferase activity measured with atrazine as substrate was 4.4- and 3.6-fold greater in leaf and stem tissue, respectively, of the resistant biotype. Kinetic analyses of glutathione S-transferase activity in leaf extracts from the resistant and susceptible biotypes were performed with the substrates glutathione, 1-chloro-2,4-dinitrobenzene, and atrazine. There was little or no change in apparent K(m) values for glutathione, atrazine, or 1-chloro-2,4-dinitrobenzene. However, the V(max) for glutathione and atrazine were approximately 3-fold higher in the resistant biotype than in the susceptible biotype. In contrast, the V(max) for 1-chloro-2,4-dinitrobenzene was 30% lower in the resistant biotype. Leaf glutathione S-transferase isozymes that exhibit activity with atrazine and 1-chloro-2,4-dinitrobenzene were separated by fast protein liquid (anion-exchange) chromatography. The susceptible biotype had three peaks exhibiting activity with atrazine and the resistant biotype had two. The two peaks of glutathione S-transferase activity with atrazine from the resistant biotype coeluted with two of the peaks from the susceptible biotype, but peak height was three- to fourfold greater in the resistant biotype. In both biotypes, two of the peaks that exhibit glutathione S-transferase activity with atrazine also exhibited activity with 1-chloro-2,4-dinitrobenzene, with the peak height being greater in the susceptible biotype. The results indicate that atrazine resistance in the velvetleaf biotype from Maryland is due to enhanced glutathione S-transferase activity for atrazine in leaf and stem tissue which results in an enhanced capacity to detoxify the herbicide via glutathione conjugation.

Journal Article↗
PubMed1996

Atrazine retention and transport in soils.

No pesticide has been studied as extensively as atrazine. The study of atrazine has contributed to our general understanding of the behavior of pesticides in soils. New knowledge and concepts were evaluated, such as atrazine adsorption kinetics, desorption hysteresis, and preferential flow. Corresponding conceptual models were also proposed to explain the behavior of atrazine in soils. Atrazine adsorption-desorption is the major process affecting atrazine behavior in soils and is mainly affected by organic matter and soil pH. Atrazine in soils is subject to biological and chemical degradations. Hydroxyatrazine, the chemical degradation product, is more strongly adsorbed to soil than atrazine. Deethylatrazine and deisopropylatrazine, the major biological degradation products, are more mobile than atrazine. Hydrolysis of atrazine is soil-surface catalyzed and favored by low soil pH. The overall dissipation rate of atrazine was found to be pseudo first-order. Two distinct and different processes are involved in atrazine movement: slow transport through the soil matrix and rapid movement through macropores. The first process is controlled by adsorption kinetics and degradation reactions and can be well explained by models based on chemical heterogeneity, such as the two-site models and second-order models. The second flow process results from preferential flow through large pores and can be explained by physical nonequilibrium models such as the mobile-immobile and two-flow domain models. Because both processes coexist in atrazine transport, coupling of physical and chemical nonequilibrium models is often necessary and has shown promise in atrazine transport modeling. However, more efforts are needed in estimating model parameters and in developing management-oriented models.

Adsorption↗
PubMed2005

Influence of lead on atrazine uptake by rice (Oryza sativa L.) seedlings from nutrient solution.

BACKGROUND: Atrazine is a widely used herbicide, and its persistence in soil and water causes environmental concerns. In the past, plant uptake processes are mainly investigated for single contaminants. However, in many cases, contaminants co-exist in environmental matrix, such as soil, and plant uptake of one contaminant may be influenced by its co-existing ones. METHODS: The uptake of atrazine by rice seedlings (Oryza sativa L.) from nutrient solution through the roots was investigated in a solution culture, over an exposure period of 4 weeks. Atrazine accumulation in plant tissues was determined by gas chromatography, and lead was determined using atomic absorption spectrometry. RESULTS AND DISCUSSION: With different ratios of atrazine and Pb2+ concentrations in solution, the observed atrazine concentrations in shoots and roots varied significantly. In atrazine-Pb2+ mixture systems, the added Pb2+ either increased or decreased the concentrations or BCFs of atrazine in seedlings (relative to those without Pb2+), depending on the atrazine-Pb2+ ratio in nutrient solution. The enhanced atrazine uptake results presumably from atrazine-Pb2+ complex formation. The reduced atrazine uptake, which occurred mainly at high atrazine concentrations, is attributed to atrazine toxicity that inhibited seedling growth and transpiration. CONCLUSION: The formation of atrazine-Pb2+ complex both in the solution and within plant tissues may affect the accumulation of both contaminants by rice plants.

Atrazine↗
PubMed2001

Atrazine degradation by bioaugmented sediment from constructed wetlands.

The potential to establish pesticide biodegradation in constructed wetland sediment was investigated. Under microcosm conditions, bioaugmentation of sediment with small quantities of an atrazine spill-site soil (1:100 w/w) resulted in the mineralization of 25-30% of 14C ethyl atrazine (1-10 microg g(-1) sediment) as 14CO2 under both unsaturated and water-saturated conditions; atrazine and its common metabolites were almost undetectable after 30 days incubation. By comparison, unbioaugmented sediment supplemented with organic amendments (cellulose or cattail leaves) mineralized only 2-3% of 14C ethyl atrazine, and extractable atrazine and its common metabolites comprised approximately 70% of the original application. The population density of atrazine-degrading microorganisms in unbioaugmented sediment was increased from approximately 10(2)/g to 10(4)/g by bioaugmentation (1:100 w/w), and increased by another 60-fold (6.0x10(5) g(-1)) after incubation with 10 microg g(-1) of atrazine. A high population of atrazine degraders (approximately 10(6) g(-1)) and enhanced rates of atrazine mineralization also developed in bioaugmented sediment after incubation in flooded mesocosms planted with cattails (Typha latifolia) and supplemented with atrazine (3.2 mg l(-1), 1 microg g(-1) sediment). In the absence of atrazine, neither the population of atrazine degraders, nor the atrazine mineralizing potential of bioaugmented sediment increased, regardless of the presence or absence of cattails. Bioaugmentation might be a simple method to promote pesticide degradation in nursery run-off channeled through constructed wetlands, if persistence of degraders in the absence of pesticide is not a serious constraint.

Atrazine↗
PubMed2004

Relationship between uptake capacity and differential toxicity of the herbicide atrazine in selected microalgal species.

Microalgal species vary in their sensitivity to the triazine herbicide, atrazine. This study examined both atrazine uptake and cellular characteristics of microalgae to determine if either can be used to predict algal sensitivity. Standard toxicity tests were performed on five microalgal species, each representing a different algal division or habitat. Test species listed in order of increasing sensitivity were: Isochrysis galbana, Dunaliella tertiolecta, Phaeodactylum tricornutum, Pseudokirchneriella subcapitata, and Synechococcus sp. Each species was exposed to 14C-atrazine at its growth rate EC50 concentration (44-91 microg/L). At five time-points over 96 h, samples were filtered to collect algae and washed with unlabeled atrazine to displace labeled atrazine loosely absorbed to the cell surface. Radioactivity present on filters and in the growth medium was measured by liquid scintillation counting. Relationships between algal species-sensitivity to atrazine and compound uptake, cell dry weight, cell volume, and cell surface area were determined by linear regression analysis. Cell size measurements (based on dry weight, biovolume, and surface area) were significantly correlated with atrazine uptake (R2 > 0.45, P-value < 0.05). There was a significant correlation between atrazine uptake and species-sensitivity to atrazine (R2 = 0.5413 , P-value = 0.0012). These results indicate that smaller cells with greater surface area to volume ratios will incorporate more atrazine, and in general, will be more sensitive to atrazine exposure. However, I. galbana, with small cell size and relatively high atrazine uptake was the least sensitive species tested. This species and others may have mechanisms to compensate for atrazine stress that make predicting responses of microalgal communities difficult.

Atrazine↗
PubMed1997

Determination of atrazine levels in whole saliva and plasma in rats: potential of salivary monitoring for occupational exposure.

Current biological monitoring techniques are often unable to provide accurate estimates of pesticide dose in exposed worker populations. This study was conducted to investigate the feasibility of pesticide biomonitoring using saliva. Atrazine [2-chloro-4-ethylamino-6-(isopropylamino)-s-triazine], a member of the triazine herbicides, was selected to investigate salivary excretion following direct gastric administration in rats. Concentrations of atrazine in whole saliva and arterial plasma samples were determined by enzyme-linked immunosorbent assay (ELISA). Atrazine reached its highest level in both arterial plasma (238 micrograms/L) and whole saliva (157 micrograms/L) 35 min after administration of 105 mg/kg of atrazine, and then decreased with time in a parallel fashion. Although saliva atrazine levels were lower than levels in arterial plasma, there was a very high correlation between whole saliva and arterial plasma atrazine concentrations (r2 = .95). In addition, pharmacokinetic analysis suggested that salivary levels of atrazine can be used to predict concentrations of atrazine in plasma. The mean whole saliva/arterial plasma atrazine concentration ratio (S/P) was 0.66 +/- 0.11 (n = 20). The S/P ratios did not vary significantly over time, and were not affected by salivary flow rate. This study demonstrates that atrazine is transported into saliva, and that a relatively constant concentration ratio between whole saliva and arterial plasma is maintained. Because the salivary concentrations of atrazine are independent of variation in salivary flow rate, salivary monitoring of atrazine in humans may prove useful and practical. Finally, this study suggests that other pesticides with chemical and physical properties similar to those of atrazine can be monitored in saliva.

Animals↗