Development of an immunochemical detection method for atrazine-induced albumin adducts.

Atrazine (2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine) is one of the most commonly used herbicides in the United States. Exposures in rodent models have led to a host of biological effects, most notably the suppression of luteinizing hormone surge. Previously, we have reported that diaminochlorotriazine (DACT), an atrazine metabolite, forms a covalent adduct with rat hemoglobin at Cys-125. In the present study, we investigated the formation of a similar covalent adduct at Cys-34 of rat and human albumins following atrazine exposure using MALDI-TOF/TOF MS and adduct-specific immunochemical detection. Using mass spectrometry, a covalent adduct with a mass of 110 Da was located on Cys-34 of albumin from rats exposed to 20, 50, 100, and 200 mg/kg atrazine as well as rat and human albumins exposed in vitro to 90 microg/mL DACT. On the basis of the formation of the adduct in vitro, the adduct structure is a dechlorinated diaminochlorotriazine. To further study this unique protein adduction, we collaborated with Strategic Biosolutions Inc. to generate a polyclonal antibody specific for the DACT adduct and report its use for immunochemical detection. We detected adduct formation in purified serum albumin samples from rats given 5, 10, 20, 50, 100, and 200 mg/kg atrazine as well as rat and human albumins exposed in vitro to 90 microg/mL DACT by using immunochemical analysis. No adducts were detected in control animals or in the in vitro controls using our immunochemical detection method. In summary, these data report the development of a novel immunochemical detection system that could provide a rapid screening methodology for the detection of atrazine in exposed human populations.

Identification of a novel hemoglobin adduct in Sprague Dawley rats exposed to atrazine.

Atrazine (2-chloro-4-[ethylamino]-6-[isopropylamino]-1,3,5-triazine) is one of the most commonly used herbicides in North America and is frequently detected in ground and surface waters. This research investigated possible covalent modifications of hemoglobin following in vivo exposures to atrazine in Sprague Dawley (SD) rats and in vitro incubations with diaminochlorotriazine. SD rats were exposed to 0, 10, 30, 100, and 300 (mg atrazine/kg)/day for 3 days via oral gavages, and blood was drawn at 0 h, 24 h, 72 h, 20 days, 1 month, and 2 months for globin analysis. Globin was purified from red blood cells, separated with high-performance liquid chromatography, and analyzed with matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS). An additional beta globin peak was seen in exposed animals during the HPLC and MALDI-TOF MS analysis with a mass 110 Da greater than the normal beta subunits. Tryptic digests of this beta peak contained a peptide of 1449.9 m/z that corresponded to a modified peptide of amino acids 121-132. Mass spectrometry sequencing of this peptide indicated a 110 Da addition to Cys-125 of the major beta globin chain, which corresponds to a nucleophilic substitution reaction with a diaminochlorotriazine. In vitro incubations of SD globin and diaminochlorotriazine also resulted in a peptide of 1449.6 m/z that was identical in sequence to the modified peptide seen in the in vivo digest, confirming the nucleophilic substitution mechanism of adduct formation. Exposures of SD rats to atrazine results in formation of an adduct that is easily detected and provides an analytical model for detection of triazine adducts in other macromolecules with sulfhydryl functional groups.