Efecto de un herbicida a base de glifosato sobre la generación de alteraciones metabólicas sistémicas y cambios histológicos hepáticos en un modelo animal de insulinorresistencia / Effects of a glyphosate-based herbicide on systemic metabolic alterations and histologic hepatic changes present in an animal model of insulin resistance

Introducción: el estrés oxidativo y la inflamación asociados a la insulinorresistencia (IR) contribuyen a generar esteatohepatitis no alcohólica. También la exposición al glifosato, un herbicida ampliamente utilizado, incrementa la peroxidación lipídica hepática con aumento de radicales libres de O2. Objetivos: evaluar los efectos de la administración prolongada de un herbicida a base de glifosato sobre la generación de IR, estrés oxidativo y cambios histológicos hepáticos en animales tratados con una dieta rica en sacarosa (DRS). Metodología: ratas Wistar macho (~300 g) recibieron Credit® por vía intraperitoneal (~50 mg/kg de glifosato tres veces por semana; grupo G, n=6), sacarosa al 30% en el agua de bebida (grupo S, n=6), ambos tratamientos (grupo G+S, n=8), o ninguno de ellos (grupo C, n=7). Tras una exposición de 8-10 semanas se midieron glucemia e insulinemia basales y tras una carga de glucosa intraperitoneal. En la semana 13, tras la eutanasia, se extrajo el hígado (tinciones con hematoxilina-eosina y tricrómica de Masson, TBARS). Resultados: no hubo diferencias significativas en los niveles glucémicos basales o postcarga. Los tratamientos con G o S generaron incrementos leves de la IR evidenciados por el índice HOMA-IR, mientras que la combinación de G+S llevó a un aumento altamente significativo de este parámetro. También fue más marcado, en estos animales, el grado de lipoperoxidación (TBARS) medido en homogenatos hepáticos. La evaluación histológica mostró signos de esteatosis y fibrosis en los grupos G y G+S, e infiltrados inflamatorios en todos los grupos tratados. Conclusiones: aislado o en combinación con sacarosa, el herbicida a base de glifosato aumentó el grado de esteatosis y fibrosis a nivel hepático. Por otro lado, la administración del herbicida incrementó la magnitud de la insulinorresistencia inducida por la DRS generando un mayor estrés oxidativo a nivel hepático

Plasma esterases in the tegu lizard Tupinambis merianae (Reptilia, Teiidae): impact of developmental stage, sex, and organophosphorus in vitro exposure.

PURPOSE: In this study, we determined normal serum butyrylcholinesterase (BChE) and carboxylesterase (CbE) activities in Tupinambis merianae in order to obtain reference values for organophosphorus pesticide monitoring. METHODS: Forty-two T. merianae individuals were grouped by sex and size to identify potential differences in their enzyme levels to allow for proper representation of normal values for females, males, juveniles, and hatchlings. Mean CbE was determined using two model substrates: alpha-naphtylacetate (α-NA) and p-nitrophenyl valerate (4-NPV). BChE and CbE sensitivity to malaoxon (Mx) was also evaluated as well as the possibility of BChE reactivation with pyridine-2-aldoxime methochloride (2-PAM). RESULTS: Mean adult females' BChE was significantly higher than adult males, juveniles, and hatchlings. No significant differences were found between groups regarding CbE. CbE (4-NPV) activity showed slightly negative correlation with lizard snout-vent length, while BChE and CbE (α-NA) showed no correlation with body size. Apparent IC(50) values for BChE and CbE (α-NA) suggested different sensitivities among groups. CbE (4-NPV) could not be inhibited. All Mx-inhibited groups treated with 2-PAM in a final concentration of 2.8 mM showed clear signs of reactivation. CONCLUSIONS: In conclusion, the results demonstrate that (1) plasma esterase activity did not vary with age and sex, except for BChE activity, and (2) because biological and environmental variables could be confounding factors in the response of plasma cholinesterases, complementary biomarkers like CbE inhibition and oxime-induced reactivation of esterases are strongly recommended.

Toxicity of four herbicide formulations with glyphosate on Rhinella arenarum (anura: bufonidae) tadpoles: B-esterases and glutathione S-transferase inhibitors.

In this study, amphibian tadpoles Rhinella arenarum were exposed to different concentrations of Roundup Ultra-Max (ULT), Infosato (INF), Glifoglex, and C-K YUYOS FAV. Tadpoles were exposed to these commercial formulations with glyphosate (CF-GLY) at the following concentrations (acid equivalent [ae]): 0 (control), 1.85, 3.75, 7.5, 15, 30, 60, 120, and 240 mg ae/L for 6-48 h (short-term). Acetylcholinesterase (AChE), butyrylcholinesterase (BChE), carboxylesterase (CbE), and glutathione S-transferase (GST) activities were measured among tadpoles sampled from those treatments that displayed survival rates >85%. Forty-eight-hour LC(50) for R. arenarum tadpoles exposed to CF-GLY in the static tests ranged from ULT = 2.42 to FAV = 77.52 mg ae/L. For all CF-GLY, the LC(50) values stabilized at 24 h of exposure. Tadpoles exposed to all CF-GLY concentrations at 48 h showed decreases in the activities of AChE (control = 17.50 ± 2.23 nmol/min/mg/protein; maximum inhibition INF 30 mg ae/L, 71.52%), BChE (control = 6.31 ± 0.86 nmol/min/mg/protein; maximum inhibition INF 15 mg ae/L, 78.84%), CbE (control = 4.39 ± 0.46 nmol/min/mg/protein; maximum inhibition INF 15 mg ae/L, 81.18%), and GST (control = 4.86 ± 0.49 nmol/min/mg/protein; maximum inhibition INF 1.87 mg ae/L, 86.12%). These results indicate that CF-GLY produce a wide range of toxicities and that all enzymatic parameters tested may be good early indicators of herbicide contamination in R. arenarum tadpoles.

Effects of agricultural pond eutrophication on survival and health status of Scinax nasicus tadpoles.

To test the hypothesis that eutrophication ponds modulate some aspects of the health responses and survival of anuran tadpoles, we conducted field experiments using Scinax nasicus as sentinel organism to evaluate the quality of two ponds filled with agricultural runoff in a dominant agricultural landscape of Mid-Western Entre Ríos Province (Argentina). The survival, growth and development rates, erythrocytes nuclei aberrations, parasite infection, and brain cholinesterase activity were monitored after seven days of exposure. Water samples from the ponds were also analyzed for physico-chemical variables and levels of pesticide residues. Residues of organochlorine pesticides and nutrients were higher in the agricultural ponds with respect to those from the control pond. We suggest that the interactions among washed-off nutrients and pesticides from agriculture and environmental factors account for deleterious effects on S. nasicus survival, growth and development rate, thereby compromising their health status. These effects can lead, in turn, to an increase in tadpole vulnerability to opportunistic parasites, erythrocytes nuclei aberrations or hemolysis.

Plasma B-esterase and glutathione S-transferase activity in the toad Chaunus schneideri (Amphibia, Anura) inhabiting rice agroecosystems of Argentina.

B-esterase (BChE: butyrylcholinesterase and CbE: carboxylesterase) and glutathione S-transferase (GST) activity were measured in the plasma of Chaunus schneideri collected in rice fields and surrounding environments and in a reference pristine forest. The chemical criterion based on in-vitro reactivation of BChE activity using pyridine-2-aldoxime methochloride (2-PAM) was also determined. Mean values of plasma BchE, CbE, and GST activity for samples from agricultural areas were different from those for samples from pristine forest. Plasma samples from the two agricultural areas showed positive reactivation of BChE activity after incubation with 2-PAM. Based on our experimental evidence we suggest B-esterases and gluthatione S-transferases can be used in field monitoring as biomarkers of exposure of wildlife to pesticides, because the analysis in non-destructive and is sensitive to anti-ChE agrochemicals. Chemical reactivation of BChE is also a complementary method for assessing the effects of pesticides on toads inhabiting rice fields. Further studies are urgently needed to investigate adverse effects of massive exposure to pesticides experienced by native populations of anurans.

Micronucleus induction in erythrocytes of the Hyla pulchella tadpoles (Amphibia: Hylidae) exposed to insecticide endosulfan.

Endosulfan is a synthetic chlorinated and environmental genotoxic pesticide used worldwide for crop production. We used the micronucleus test in erythrocytes of Hyla pulchella tadpoles in order to develop an experimental model for detecting genotoxic effects of the synthetic chlorinated cyclodiene endosulfan. The frequency of micronuclei was examined in blood smears obtained from tadpoles exposed in vivo to three different concentrations 2.5, 5, and 10 microg/l of the compound and fixed at two sampling times 48 and 96 h. As a positive control larvae were exposed to 40 mg/l of cyclophosphamide. Results obtained here demonstrated the genotoxic effects of the commercial formulation endosulfan in the experimental model assayed.