Cellular and Molecular Targets of Benzo[a]pyrene and Metal Toxicity in Xenopus laevis Embryos and in Hep G2 Cells
Marina Camatini, Patrizia Bonfanti, Anita Colombo, Chiara Urani and Silvia Crippa
This paper describes the use of two in vitro systems (stage 35 Xenopus laevis embryos and the human hepatoblastoma cell line, Hep G2) to study effects of some environmental contaminants (benzo[a]pyrene, copper and zinc), which are representative of chemicals with different cell targets and mechanisms of action. The ability to activate benzo[a]pyrene and to metabolise it with the cytochrome P4501A isozyme were demonstrated in both in vitro systems by assessing the formation of water-soluble and protein-bound benzo[a]pyrene metabolites and by immunochemical analysis. In X. laevis embryos, the formation of DNA adducts demonstrated the ability to produce benzo[a]pyrene reactive metabolites. Moreover, in Hep G2 cells, the cytoskeletal protein, tubulin, and the reduced form of glutathione proved to be the cellular targets of copper and zinc toxicity. In response to metal-induced stress in Hep G2 cells, there was a cytoplasmic reorganisation of heat shock protein, Hsp 70. In conclusion, the in vitro systems provide for a rapid evaluation of heterogeneous compounds such as benzo[a]pyrene and heavy metals that differ in toxic potency and mechanisms of action. They could also be used to study the mechanisms of toxic action and to identify specific cellular and molecular targets.
Shrawan K. Gupta, Richa Srivastava, Neeraj Mathur and Prem N. Saxena
To establish the use of Metaphire posthuma as a sensitive model for ecotoxicological studies, the comparative effects of five metals on the hatching profiles of the cocoons of the earthworms, Metaphire posthuma, Eisenia foetida and Perionyx excavatus, were studied. The cocoons of the three species of earthworms were exposed to copper, chromium (III), chromium (VI), lead and zinc at 1.25, 2.5, 5.0 and 10.0ppm. Viable cocoons were incubated at 20 ± 1ºC by using the immersion method. The results indicated that the inhibition of cocoon hatching was concentration dependent. The normal hatching, delayed hatching and non-viability of cocoons were recorded. At a concentration of 1.25ppm, there was almost no effect on the hatching of the cocoons of all three species of earthworms, except when exposed to chromium (VI), but higher concentrations (2.5 and 5.0ppm) caused severe effects. It was concluded that M. posthuma was more sensitive than the other two species, and that it is a suitable model for use in ecotoxicity