Protein binding of glufosinate and factors affecting it revealed by an equilibrium dialysis technique

Interpreting in vitro developmental toxicity test battery results: The consideration of toxicokinetics

In the EU collaborative project ChemScreen an alternative, in vitro assay-based test strategy was developed to screen compounds for reproductive toxicity. A toxicokinetic modeling approach was used to allow quantitative comparison between effective concentrations in the in vitro test battery and observations of developmental toxicity in vivo. This modeling strategy is based on (1) the definition of relevant observations of toxicity in vivo, (2) simulation of the corresponding systemic concentrations in vivo by toxicokinetic modeling, and (3) correction for differences in protein binding and lipid partitioning between plasma and in vitro test media. The test results of a feasibility study with a number of known reproductive toxicants has been described previously (Piersma et al. [15]). In the present paper, we take a more detailed look at the toxicokinetics of these compounds, and add the analysis of some compounds from subsequent studies. We discuss how the consideration of toxicokinetics allowed comparison between test systems with differing test medium composition, has helped to interpret the in vitro findings in light of in vivo observations, and to gain confidence in the predictive value of the test battery outcomes. The same toxicokinetic modeling strategy, in reverse order, can now be used for risk assessment purposes to predict toxic doses in vivo from effective concentrations in vitro.

Rapid determination of glyphosate, glufosinate, bialaphos, and their major metabolites in serum by liquid chromatography-tandem mass spectrometry using hydrophilic interaction chromatography

We developed a simple and rapid method for the simultaneous determination of phosphorus-containing amino acid herbicides (glyphosate, glufosinate, bialaphos) and their major metabolites, aminomethylphosphonic acid (AMPA) and 3-methylphosphinicopropionic acid (MPPA), in human serum. Serum samples were filtrated through an ultrafiltration membrane to remove proteins. The filtrate was then washed with chloroform, and injected into a liquid chromatography-tandem mass spectrometry (LC-MS/MS) system. Chromatographic separation was achieved on a hydrophilic interaction chromatography (HILIC) column. Determination of the target herbicides and metabolites was successfully carried out without derivatization or solid phase extraction (SPE) cartridge clean-up. The recoveries of these compounds, added to human serum at 0.2μg/mL, ranged from 94% to 108%, and the relative standard deviations (RSDs) were within 5.9%. The limits of detection (LODs) were 0.01μg/mL for MPPA, 0.02μg/mL for AMPA, 0.03μg/mL for both glyphosate and glufosinate, and 0.07μg/mL for bialaphos, respectively.

Severe acute poisoning due to a glufosinate containing preparation without mitochondrial involvement

Glufosinate is a non-selective herbicide widely used in domestic gardens and agriculture. Few cases of glufosinate poisoning have been reported although there has been an increase in recent years, particularly in Japan. Glufosinate toxicity is related to its capacity to inhibit glutamine synthetase and glutamate decarboxylase, which may lead to a potentially fatal multiorgan failure. We report the case of a 41-year-old woman who ingested between 30 and 50 mL of a herbicide (Finale®) containing glufosinate (14%) in a suicide attempt. One hour after ingestion, the patient attended the Emergency Department of her own volition. Her overall status was good, and the physical examination was unremarkable. Gastric lavage was carried out, 25 g of activated charcoal was administered, and the patient was admitted for observation. Seventeen hours later, the patient presented drowsiness and a sinus bradycardia of 40 bpm. Thirty-two hours after ingestion, the Glasgow Coma Score was 8, and orotracheal intubation and mechanical ventilation were begun. At 3 days, the patient presented a self-limiting episode of ventricular tachycardia. She recovered consciousness progressively and was extubated without complications. The evolution was favorable, but the sinus bradycardia persisted up to 8 days after the ingestion. A study of lymphocyte mitochondrial function showed no alteration in mitochondrial oxidative capacity or the enzymatic activity of the complexes of the electron transport chain. A small ingestion of glufosinate can cause severe poisoning, whose manifestations predominantly involve the central nervous system and heart rhythm. Signs and symptoms may not appear for several hours and may persist for several days. In spite of these multi-organ manifestations, no alteration in lymphocyte mitochondrial function has been reported.

Quantitative determination of glufosinate in biological samples by liquid chromatography with ultraviolet detection after p-nitrobenzoyl derivatization

We have established a new HPLC method for derivatizing and quantifying glufosinate (GLUF) in human serum and urine using p-nitrobenzoyl chloride (PNBC). The p-nitrobenzoyl derivative of GLUF (PNB-GLUF) was produced quantitatively over 10 min at room temperature. PNB-GLUF possesses the property of ultraviolet (UV) light absorption with a lambda(max) of 272.8 nm, and was isolated from biological specimens by reversed-phase chromatography using Inertsil Ph-3. In experiments at a UV wavelength of 273 nm, GLUF has a quantitative detection limit of 0.005 microg/ml, and when it was added to both serum and urine to yield concentrations of 0.1-1000 microg/ml, its recovery rate was quite satisfactory: at least 93.8% in all cases. Further, the measured amounts of GLUF in 23 serum samples from patients intoxicated by ingestion of GLUF compared favorably with those obtained by fluorescence derivatization-HPLC using 9-fluorenylmethyl chloroformate (R=0.998). This technique of analysis is, in addition, applicable for Glyphosat, which possesses a chemical structure resembling that of GLUF, and it will be of great use in the determination of these two compounds.