Levels of plasma B-esterase and Glutathione-S-transferase activities in three South American toads.

LAJMANOVICH R. C.; SÁNCHEZ-HERNÁNDEZ J.C.; PELTZER P.M; ATTADEMO A.M; FIORENZA G.S; CABAGNA M.C.; BASSÓ A.

Toxicology Environmental and Chemistry

Taylor & Francis

Año: 2008 p. 1145 - 1161

1029-0486

We determined the normal levels of butyrylcholinesterase (BChE), carboxylesterase(CbE), and glutathione S-transferases (GST) activities in three SouthAmerican toad species in order to establish reference values for field pesticidemonitoring purposes. Interspecies variations in B-esterase and GST activitieswere examined according to body mass. In addition, comparative inhibition ofBChE and CbE activities using malaoxon, and chemical reactivation ofmalaoxon-inhibited BChE activity using pyridine-2-aldoxime methochloride(2-PAM) were investigated. Bufo fernandezae had average activity values forBChE: 17.31 mmol min
1 ml
1; CbE: 621.49 nmol min
1 ml
1 and GST:1.94 mmol min
1 ml
1 while B. arenarum enzymatic average activities wereBChE: 9.51 mmol min
1 ml
1; CbE: 270.07 nmol min
1 ml
1, and GST:1.59 mmol min
1 ml
1; finally Bufo schneideri had enzymatic mean values ofBChE: 2.08 mmol min
1 ml
1; CbE: 301.95 nmol min
1 ml
1, and GST:1.60 mmol min
1 ml
1. Moreover, we found an allometric relationship betweenplasma BChE and CbE activities and body size for the three toad species. Wesuggest that B. fernandezae would be the species with a higher tolerance capacityto organophosphorous insecticides compared to the other toad species, while B.schneideri may be the most vulnerable toad species to field pesticide exposure,although some other factors (e.g., brain AChE sensitivity or pesticide metabolismby phosphotriesterases) should be also taken into account. The malaoxoninhibitedBChE activity of the three toad species was reactivated in the presenceof 2-PAM, and it is recommended as a specific and sensitive methodology in theassessment of field exposure to OP insecticides together to compare BChE activitylevels between OP-exposed and nonexposed individuals.