RESUMO
The interaction of methyl-parathion with the albumin of Piaractus mesopotamicus (Holmberg 1887) (= pacu), a fish species typical of Brazilian rivers, was studied and the results compared with known values for human and bovine albumin obtained in an earlier investigation. Methyl-parathion (O,O-dimethyl O-p-nitrophenyl phosphorothioate) is an organophosphorous pesticide still used in agriculture and fish farming in many countries. The fluorescence quenching technique with tryptophan as a natural probe was used to detect for the presence of methyl-parathion. Fluorescence can be mathematically expressed by the Stern-Volmer equation to calculate quenching constants, and changes in the behavior of Stern-Volmer curves at different temperatures indicate the nature of the mechanism causing the quenching. Our results indicate that methyl-parathion forms a complex with fish albumin. The estimated association constant is 9.73 x 103 (+/- 4.9 x 102) M(-1) at 25 degrees C.
Assuntos
Peixes/metabolismo , Inseticidas/metabolismo , Metil Paration/metabolismo , Albumina Sérica/metabolismo , Animais , Bovinos , Fluorescência , Humanos , Modelos Biológicos , Especificidade da Espécie , Espectrofotometria Ultravioleta , Temperatura , TriptofanoRESUMO
The interaction of methyl-parathion with serum and albumin of pacu, Piaractus mesopotamicus, was studied, using the fluorescence quenching technique. Pacu is a neo-tropical fish specie inhabitant of rivers from western regions of Brazil. Methyl-parathion (O,O-dimethyl O-p-nitrophenyl phosphorothioate) is an organophosphorous pesticide still used in agriculture and fish farming in many countries. The quenching of fluorescence can be mathematically expressed by the Stern-Volmer equation to calculate quenching constants. Stern-Volmer curves analysis is able to give important information about the pesticide-albumin interaction. Our results showed that the serum quenching reached 10% when the molar ratio of pesticide/albumin was about 7:1 for the three temperatures of the experiment. For the pure albumin quenching of 10%, methyl-parathion concentrations were 6, 7 and 9 times higher than albumin at 20, 25 and 30 degrees C, respectively. The calculated Stern-Volmer constants at 25 degrees C were 9.73x10(3)(+/-4.9x10(2))M(-1) for serum and 9.20x10(3)(+/-2.0x10(2))M(-1) for albumin. It was observed that albumin quenching is the phenomenon contributing to the quenching of the pacu serum fluorescence for methyl-parathion concentration lower than 10microM, suggesting that the protein is the most important carrier for the pesticide in serum.
Assuntos
Peixes/sangue , Inseticidas/metabolismo , Metil Paration/metabolismo , Albumina Sérica/metabolismo , Animais , Proteínas Sanguíneas/análise , Fluorescência , Ligação Proteica , Albumina Sérica/análiseRESUMO
BACKGROUND: Chronic administration of furosemide may induce thiamine deficiency and cause or aggravate myocardial dysfunction. METHODS AND RESULTS: Wistar rats were divided into four groups according to food and treatment: (1) thiamine standard chow with intraperitoneal furosemide administration; (2) thiamine standard chow with intraperitoneal saline administration; (3) thiamine-deficient chow with intraperitoneal furosemide administration; and (4) thiamine-deficient chow with intraperitoneal saline administration. Thiamine status was evaluated by high-performance liquid chromatography determination in plasma, erythrocytes, and myocardium, and by erythrocyte transketolase activity and the thiamine pyrophosphate effect to recover transketolase activity. Left ventricular mass index, intramyocardial arteries-to-cardiomyocyte ratio, cardiomyocyte cross-sectional area, and cardiomyocyte nuclei number were estimated. Myocardial structure was also studied by transmission electronic microscopy. Group 3 showed significantly lower blood and myocardial thiamine levels, which was not observed in group 1. Left ventricular mass index, cardiomyocyte cross-sectional area, and intramyocardial arteries-to-cardiomyocyte ratio were smaller in thiamine-deficient and furosemide-treated rats. However, no significant variation was found in the number of cardiomyocyte nuclei among the groups. Transmission electronic microscopy showed mitochondrial alterations in the thiamine-deficient groups. CONCLUSION: The present results indicate that furosemide administration is not the primary cause of thiamine deficiency in rats with adequate thiamine intake. Furosemide aggravates thiamine deficiency only in situations associated with insufficient thiamine intake, causing cardiac structural alterations, such as myocardial fiber hypotrophy, poor microvascularization, and mitochondrial degeneration.
Assuntos
Cardiomiopatias/induzido quimicamente , Diuréticos/efeitos adversos , Furosemida/efeitos adversos , Miocárdio , Deficiência de Tiamina/diagnóstico , Animais , Cardiomiopatias/etiologia , Diuréticos/administração & dosagem , Diuréticos/farmacologia , Furosemida/administração & dosagem , Furosemida/farmacologia , Nível de Saúde , Masculino , Estado Nutricional , Ratos , Ratos Wistar , Fatores de Risco , Deficiência de Tiamina/etiologiaRESUMO
Brain acetylcholinesterase (AChE) of some fishes from the coast of Rio de Janeiro State was studied as a possible pesticide biomarker in marine environmental monitoring. AChE specific activity in brain varied from 145 to 530 U/g of proteins and the Michaelis-Menten constant (K(M)) for acetylthiocholine varied from 104 to 291 microM among the 20 species studied. The enzyme sensitivity to methyl paraoxon, evaluated by the inhibition kinetic constants, shows that some species (Paralonchurus brasiliensis and Genidens genidens) are more sensitive (IC50-30 min=455 and 468 nM, respectively). The less sensitive Merluccius hubbsi and Percophis brasiliensis (IC50-30 min=3339 and 3259 nM, respectively) belong to the super-order Paracanthopterygii, which includes the more ancient species. On the other hand, more susceptible species belong to the super-order Acanthopterygii, which includes more recent species. These results suggest a possible evolutionary linkage for AChE sensitivity to methyl paraoxon. The application of inhibition kinetic constants for fish brain AChE in phylogenetic studies is still being investigated. The results have shown that a fish sentinel species should have the highest brain AChE level among the more sensitive ones.
Assuntos
Acetilcolinesterase , Biomarcadores/análise , Encéfalo/enzimologia , Monitoramento Ambiental/métodos , Peixes/metabolismo , Praguicidas/análise , Poluentes Químicos da Água/análise , Acetilcolinesterase/análise , Animais , Oceano Atlântico , Brasil , Inibidores da Colinesterase/metabolismo , Análise por Conglomerados , Concentração Inibidora 50 , Cinética , Paraoxon/análogos & derivados , Paraoxon/metabolismo , Filogenia , Especificidade da EspécieRESUMO
Methyl parathion (MP; O,O-dimethyl O-p-nitrophenyl phosphorothioate) is an organophosphorous compound still largely used in agriculture and fish hatcheries. This pesticide is not quite selective and is potentially toxic for both vertebrates and invertebrates. Its mechanism of acute toxicity is the inhibition of the enzyme acetylcholinesterase in nervous tissue. Binding of pesticides to plasma proteins is one of many factors that influence their distribution and elimination. The free concentration available for toxic action can be effectively reduced for pesticides with high binding to plasma proteins, although the affinity of pesticides to plasma proteins is often lower than for the enzyme targets. Several different transport proteins exist in blood plasma, but albumin only is able to bind a wide diversity of xenobiotics reversibly with high affinity. It was already known that parathion (ethyl parathion) exhibits a high affinity to human and bovine serum albumins. We studied interactions of methyl parathion with these albumins by using fluorescence quenching techniques. We selectively excited the fluorescence of tryptophan residues with a 290 nm wavelength light, and observed quenching by titrating human and bovine serum albumin solutions with methyl parathion. Stern-Volmer graphs were plotted and quenching constants were estimated. Our results pointed to the formation of complexes of methyl parathion with albumins. Association constants at 25 degrees C were 3.07 x 10(4) (1.2 x 10(3))M(-1) for human serum albumin, and 1.96 x 10(4) (+/- 4.5 x 10(2))M(-1) for bovine serum albumin. At 37 degrees C, they were 1.08 x 10(4) (+/- 2.0 x 10(2))M(-1) for human serum albumin, and 8.16 x 10(3) (+/- 1.9 x 10(2))M(-1) for bovine serum albumin. Results also suggest that the primary binding site for methyl parathion on albumin is close to tryptophan residues 214 of human serum albumin and 212 of bovine serum albumin.