Detoxifying metabolism for the pesticide azinphos methyl in the Patagonian silverside

GUERREÑO M.; PAREDES E.; LUQUET C; VENTURINO A

Rosario

Congreso; L Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2014

SAIB

The intensive fruit production in Río Negro valley leads to the massive use of organophosphate (OP) pesticides. Our objective was to study the detoxifying metabolism of the OP azinphos methyl (AZM) in the Patagonian silverside (Odontesthes hatcheri). Juvenile fish were exposed to 0.1-10 μg/L AZM during 96h. The LC50 was 0.174±0.076 μg/L AZM, 10 times lower than maximum environmental concentrations. Target organs showed diverging toxodynamics; while brain acetylcholinesterase (AChE) was inhibited (IC50 = 0.193±0.063 μg/L), with low carboxylesterase (CabE) activity unaffected by AZM, the opposite was found in muscle, with buffer CabE (40% inhibition, p<0.001) that prevented AChE inhibition. GSH increase as antioxidant response was elicited in both (2X, p <0.05). CabE was also inhibited in intestine (70%, p<0.001), but hepatic detoxifying response was induced through CabE (150%, p<0.005) and GSH increase. GSH-S-transferase (GST) activity was inhibited by 50% in liver and intestine (p<0.05), showing that oxidative stress indeed affected the detoxifying capacity. Multiple Xenobiotic Resistance (MXR) capacity was analyzed by ex vivo assay of conjugated DNP-S-GSH transport dependant on GST conjugating activity. AZM caused an increase of 182% (p<0.001) in liver slices, while 50% of decrease was found in intestine (p<0.05), suggesting organ-specific effects on the excretory capacity.