Plasma B-esterase and Glutathione S-transferase Activities in the South American Reptiles Caiman latirostris (Crocodylia, Alligatoridae) and Phrynops hilarii (Testudines, Chelidae)

Abstract

We determined normal plasma butyrylcholinesterase (BChE), carboxylesterase (CbE using α-NA substrate), and glutathione S-transferase (GST) activities in Caiman latirostris and Phrynops hilarii to obtain reference values for organophosphorus (OP) pesticide monitoring. BChE and CbE sensitivity to malaoxon was also evaluated. C. latirostris (N = 12; six males and six females) and P. hilarii (N = 12; seven males and five females) were obtained from the programs Yacare (Entre Rios Province, Argentina) and Zoo of Cordoba (Cordoba Province, Argentina). Mean total (female and male) plasma BChE activity was significantly different between reptile species, ranging between 0.337 ± 0.085 μmol min−1 ml−1 of plasma for C. latirostris and 0.251 ± 0.070 μmol min−1 ml−1 of plasma for P. hilarii. However, plasma CbE (α-NA) and GST activities were significantly higher in P. hilarii (4.81 ± 1.00 and 0.145 ± 0.045 μmol min−1 ml−1 of plasma, respectively) than in C. latirostris (0.57 ± 0.20 and 0.059 ± 0.013 μmol min−1 ml−1 of plasma, respectively). No significant differences in B-esterase and GST activities were detected between sexes, except CbE (α-NA) for C. latirostris. IC50 values for BChE and CbE (α-NA) suggested different sensitivity levels between species and between sexes. The results demonstrate that plasma esterase activity varied between species, but not between sexes (except CbE for C. latirostris). The in vitro inhibition tests indicated that CbE (α-NA) is more sensitive to inhibition than BChE. C. latirostris may be the reptile species most vulnerable to field pesticide exposure because this reptile presents the lowest CbE activity levels and its B-esterase levels seem more sensitive to OP.