RESUMO
The 96-h LC(50) value of carbaryl was 14.6 microg/mL for the snail Pomacea patula. Organisms were exposed for 72 h to a low sublethal concentration (0.1 of LC(50)) using a semistatic contamination system; bioconcentration and elimination experiments were performed evaluating simultaneously acetylcholinesterase (ACHase) activity. The inhibition of the digestive gland ACHase reached 76% when the carbaryl concentration in tissue was 3.2 microg/g. The increased enzyme inhibition was observed concomitantly with the bioconcentration of carbaryl until 7 h. ACHase inhibition was linearly dependent on the uptake and bioconcentration of carbaryl (r(2)=0.87). The transfer of snails to carbaryl-free water after 72 h of exposure was followed by rapid monophasic elimination with a half-life of 1.0 h. However, ACHase activity levels never returned to control values. These results revealed that the bioconcentration might play a critical role in contributing to the toxicity of carbaryl.
Assuntos
Carbaril/toxicidade , Inibidores da Colinesterase/toxicidade , Inseticidas/toxicidade , Animais , Carbaril/farmacocinética , CaramujosRESUMO
Toxicity and uptake data for Limnodrilus hoffmeisteri generated by nickel in systems using three natural sediments (trout farms: El Oyamel, El Truchón, and El Potrero), are presented. Nickel uptake and hemoglobin concentration were studied in L. hoffmeisteri exposed to spiked sediments. Nickel concentration and its toxic effect on hemoglobin were used as indicators of exposure. Sediment texture was also considered. Hemoglobin concentration decreased after treatment with nickel. The hemoglobin concentration test indicated a response to the bioavailability of nickel. This investigation clearly documents that sediments of El Truchón, El Oyamel, and El Potrero exhibit a toxicity potential. These results suggest the usefulness of diversity of bioassays for evaluating the toxicity of sediments polluted with heavy metals.