Stress responses to carbaryl and organophosphates in toad larvae

FERRARI ANA; LASCANO CECILIA; PECHÉN DE DANGELO ANA M; VENTURINO ANDRÉS

Iguazú, Misiones, Argentina

Congreso; XXXVV Reunión Anual de la Sociedad Argentina de Investigacion Bioquímica y Biología Molecular (SAIB); 2004

SAIB

Carbaryl (CB), a carbamate insecticide vastly used in Argentine, acts primarily on acetylcholinesterase (AChE), the same target as organophosphates (OP). However, secondary effects described for aquatic species, i.e. alteration of antioxidant system, differ in both families of pesticides. Our objective is to compare these targets in CB-exposed and OP-exposed toad larvae. Bufo arenarum larvae were exposed up to 48 h to 5-20 mg/l CB. The activity of AChE, aliesterase, antioxidant enzymes glutathion-S-transferase (GST), catalase (CAT) and glutathione reductase (GR), and reduced (GSH) and oxidized (GSSG) glutathione were analysed. Similar data were obtained for the OP malathion and azinphos methyl. Esterases were inhibited by CB (60-90%) similarly as described for fish by us. GSH level was diminished after 24 h (38-72%) and oxidized to GSSG, but it recovered at 48 h. CAT and GST were induced by CB at 48 h, while GR remained unchanged. OP decreased both GSH and GSSG levels persistently at 48 h, induced GST and inhibited CAT and GR. CB induce a transient oxidative stress in Bufo arenarum larvae by depleting GSH, which is overcome at 48 h by induction of CAT and GST as antioxidant mechanisms. Our scope is now to evaluate if these responses are linked to aryl receptor AhR and up-regulation of XRE (xenobiotic)-dependent genes and secondary gene upregulation through. Antioxidant RE. On the other hand, both OP are demethylated by GST via GSH, and the oxidative stress caused by ROS is high enough to inactivate CAT and downregulate GR.