RESUMO
Reduced glutathion (GSH) content and glutathione S-transferase (GSH S-transferase) activity were investigated in developing toad embryos exposed to parathion, malathion, lindane and dieldrin. The embryonic GSH content was reduced after 96 h of incubation with 20.00 ppm malathion and 2.00 ppm lindane. Parathion and dieldrin did not produce any change. A similar effect was obtained in advanced stages of development (6-days larvae), but only with malathion. No correlation between the decrease in GSH level and mortality or morphologic abnormalities was observed. The four pesticides increased the activity of GSH S-transferase indicating that the enzyme is susceptible to induction during early development. The higher effect depicted by malathion may be related with an enhanced conjugation of the pesticide. Both GSH decrease and GSHS-transferase induction modifies the cell redox status and may indirectly influence transcription and translation. The early expression of GST genes provides the embryo with a useful mechanism for the regulation of tolerance against chemical stress.
Assuntos
Bufo arenarum/fisiologia , Tolerância a Medicamentos , Embrião não Mamífero/fisiologia , Glutationa Transferase/metabolismo , Glutationa/metabolismo , Praguicidas/toxicidade , Animais , Blastocisto/efeitos dos fármacos , Bufo arenarum/embriologia , Dieldrin/toxicidade , Relação Dose-Resposta a Droga , Embrião não Mamífero/efeitos dos fármacos , Indução Enzimática/efeitos dos fármacos , Gástrula/efeitos dos fármacos , Hexaclorocicloexano/toxicidade , Larva , Malation/toxicidade , Paration/toxicidade , Pigmentação da Pele/efeitos dos fármacosAssuntos
Bufo arenarum/embriologia , Dieldrin/toxicidade , Poluentes Químicos da Água/toxicidade , 5'-Nucleotidase/efeitos dos fármacos , Adenosina Trifosfatases/efeitos dos fármacos , Animais , Comportamento Animal/efeitos dos fármacos , Embrião não Mamífero/efeitos dos fármacos , Embrião não Mamífero/metabolismo , Fosfolipídeos/metabolismoRESUMO
Newly fertilized Bufo arenarum Hensel embryos were exposed continuously or for a brief period (72-120 hr) to malathion (44 ppm) and then resuspended in amphibian Ringer's solution. Continuous exposure depressed acetylcholinesterase (EC 3.1.1.7), butyrylcholinesterase (EC 3.1.1.8) and carboxylesterase (EC 3.1.1.1) activities. The activities of the three enzymes in embryos treated for 72 hr recovered after a delay of 24 hr, but these enzymes showed different rates of recovery in embryos treated for 120 hr. Acrylamide disc electrophoresis showed several bands of esterase activity in control embryos. Continuous exposure to malathion abolished all esterase activity within 48 hr, but if the exposure continued new bands of esterase activity appeared at 120 hr of exposure. The zymograms of embryos exposed for 72 or 120 hr to malathion and then transferred to uncontaminated medium for 120 hr were similar to that of control embryos.