RESUMO
In this study, teleostean fish Leporinus obtusidens (piava) were exposed to different concentrations of Roundup, a glyphosate (acid equivalent) herbicide: 0 (control), 3, 6, 10, and 20 mg/L for 96 h (short-term). Acetylcholinesterase (AChE) activity was verified in brain and muscle tissues. Metabolic parameters in the liver and muscle (lactate, glycogen, glucose, protein, and ammonia), as well as some hematological parameters, were determined. Unexposed fish exhibited significantly higher brain AChE activity when compared to that of the muscle (P<0.05) (13.8+/-0.76 and 6.1+/-1.31 micromol/min/g protein, respectively). Results indicated that AChE activity significantly decreased in the brain of fish exposed to all glyphosate concentrations tested, but in the muscle this parameter was not altered. In addition, fish exposed to all glyphosate concentrations showed a significant increase in hepatic glycogen and glucose, but a significant reduction in muscle glycogen and glucose. Lactate and protein of fish exposed to all glyphosate concentrations presented a significant decrease in the liver, but did not change significantly in the muscle. Levels of ammonia in both tissues increase in fish at all glyphosate concentrations. Exposure to this herbicide produced a decrease in all hematological parameters tested. These results indicate that AChE activity as well as metabolic and hematological parameters may be good early indicators of herbicide contamination in L. obtusidens.
Assuntos
Acetilcolinesterase/metabolismo , Proteínas Sanguíneas/metabolismo , Glicina/análogos & derivados , Herbicidas/toxicidade , Poluentes Químicos da Água/toxicidade , Animais , Contagem de Células Sanguíneas , Encéfalo/efeitos dos fármacos , Encéfalo/enzimologia , Encéfalo/metabolismo , Relação Dose-Resposta a Droga , Feminino , Peixes , Glicina/toxicidade , Fígado/efeitos dos fármacos , Fígado/enzimologia , Fígado/metabolismo , Masculino , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/enzimologia , Músculo Esquelético/metabolismo , GlifosatoRESUMO
Fingerlings of the silver catfish (Rhamdia quelen) were exposed to three herbicides widely used in rice culture in south Brazil: clomazone, quinclorac, and metsulfuron methyl. LC50 was determined and acetylcholinesterase (AChE) activity was evaluated in brain and muscle tissue of fish exposed to different herbicide concentrations after 96h (short term). The LC50 value (nominal concentration) was 7.32 mg/L for clomazone and 395 mg/L for quinclorac, but was not obtained for metsulfuron-methyl since all fingerlings survived the highest concentration of 1200 mg/L. Brain and muscle AChE activity in unexposed fish were 17.9 and 9.08 micromol/min/g protein, respectively. Clomazone significantly inhibited AChE activity in both tissues, achieving maximal inhibition of about 83% in brain and 89% in muscle tissue. In contrast, quinclorac and metsulfuron methyl caused increases in enzyme activity in the brain (98 and 179%, respectively) and inhibitions in muscle tissue (88 and 56%, respectively). This study demonstrated short-term effects of exposure to environmentally relevant concentrations of rice field herbicides on AChE activity in brain and muscle tissue of silver catfish.
Assuntos
Acetilcolinesterase/metabolismo , Sulfonatos de Arila/toxicidade , Peixes-Gato/fisiologia , Herbicidas/toxicidade , Isoxazóis/toxicidade , Oxazolidinonas/toxicidade , Quinolinas/toxicidade , Poluentes Químicos da Água/toxicidade , Animais , Encéfalo/enzimologia , Dose Letal Mediana , Músculo Esquelético/enzimologia , Oryza , SobrevidaRESUMO
We investigated NTPDase-like activity [ecto-nucleoside triphosphate diphosphohydrolases (E-NTPDases)] in liver and kidney membrane from silver catfish (Rhamdia quelen), chicken (Gallus gallus) and rat (Rattus norvegicus) under different conditions and in the presence of several inhibitors. The cation concentration required for maximal activity was 0.5, 1.5 and 2.0 mM for fish, chicken and rat liver, respectively (with ATP and ADP as substrates). The maximal activity in the kidney was observed at calcium concentrations of 0.5, 2.0, 1.5 mM (ATP) and 0.5, 1.5, 1.0 (ADP) for fish, chickens and rats, respectively. The results showed that the pH optimum for all animals and for the two tissues was close to 8.0. The temperature chosen was 25 degrees C for fish and 36 degrees C for chicken and rat preparations. Ouabain had no effect on the NTPDase-like activity of fish, chickens or rats. NTPDase activity was decreased in the presence of lanthanum in the chicken (ADP) and rat (ATP and ADP) liver. In the kidney, lanthanum inhibited fish ATP and rat ATP and ADP (0.2 mM) hydrolysis. N-ethylmaleimide (NEM) had an inhibitory effect on the kidney of all species at the concentration of 3.0 mM (ADP). Orthovanadate only inhibited fish membrane NTPDase; azide only inhibited the preparation at high concentrations (10 mM) and fluoride inhibited it at 10 mM (fish and chicken) and 5 mM (rat). Trifluoperazine (0.05-0.2 mM) and suramin (0.03-0.3 mM) inhibited NTPDase at all concentrations tested. These results suggest that NTPDase-like activity shows a different behavior among the vertebrate species and tissues studied. Additionally, we propose that NTPDase1 is the main enzyme present in this preparation.
Assuntos
Difosfato de Adenosina/metabolismo , Trifosfato de Adenosina/metabolismo , Rim/enzimologia , Fígado/enzimologia , Pirofosfatases/metabolismo , Animais , Cálcio/farmacologia , Membrana Celular/enzimologia , Galinhas/metabolismo , Inibidores Enzimáticos/farmacologia , Peixes/metabolismo , Hidrólise , Lantânio/farmacologia , Pirofosfatases/antagonistas & inibidores , Ratos , Especificidade da EspécieRESUMO
Tissue accumulation of arginine (Arg), N-acetylarginine (NA), argininic acid (AA) and homoarginine (HA) occurs in hyperargininemia, an inborn error of the urea cycle. In the present study, we investigated the in vitro effects of Arg, NA, AA and HA on NTPDase1 and 5'-nucleotidase activities from synaptosomal cerebral cortex of rats. The results showed that Arg enhances NTPDase1 activity at the high concentrations tested (1.5 and 3.0mM) for both the ATP and ADP nucleotides. Activation was also observed with other guanidino compounds tested: NA, AA and HA activated ATP and ADP hydrolysis in all experiments at the concentration of 25 microM. Besides this, NA and AA activated ATP hydrolysis at a lower concentration (1 microM). In another set of experiments, we verified the effect of Arg on purified apyrase at pH 8.0 and 6.5 and observed an increase in the enzyme activity at all Arg concentrations tested (0.01-3.0mM). In contrast, Arg and the other guanidino compounds tested did not alter 5'-nucleotidase activity. These results suggest that changes in nucleotide hydrolysis may be involved in the brain dysfunction caused by hyperargininemia amongst other potential pathophysiological mechanisms involved in this condition.