Time-concentration-dependent biochemical response to transient agrochemical exposure in tadpoles

ROSENBAUM, E.; MARCORE S; GADER, G; VENTURINO A

Puerto Madryn

Congreso; XLVI Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2010

SAIB

We have studied the biochemical response of Rhinella arenarum larvae transiently exposed 4h to 1 mg/L azinfos methyl (AM). After 4h, tadpoles suffer a mild reduction in esterase activities, mainly carboxylesterase (CE) with a slight induction of acetylcholinesterase (AChE). Induction of the Phase-II detoxification pathway is observed, through an increase in glutathione-S-transferase (GST) activity, and GSH depletion after 48h of recovery. In the present work, we deepen into time- and concentration-dependence of the biochemical response through high level and transient AM exposure (80 mg/l; 15 min). Both AChE and CE activities were deeply inhibited (20% and 80%) in transiently exposed larvae. On the contrary, neither GST nor GSH were affected by the exposure. Taken together, these results point to the varying response pattern in toad larvae, depending on the characteristic of agrochemical exposure. No Phase II detoxification metabolism would be induced by a sharp, sudden and fleeting exposure, and AM suicide sequestration by CE becomes not only the first, but the unique defense line. These results show the importance of performing a deeper characterization of the biochemical alterations in a resistant species such as the toad under different intoxication patterns. This is necessary for developing a biomonitoring tool for the evaluation of ecological impact of agrochemicals.