Stage Dependent Uptake of Cadmium in Bufo arenarum Embryos

HERKOVITS, J. AND PEREZ-COLL, C.

BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY

SPRINGER

Año: 1996 vol. 56 p. 663 - 669

0007-4861

Over the last several years, environmental contamination with cadmium hassignificantly increased because of its extensive use in anthropogenic activities. Thisheavy metal is a very toxic xenobiotic producing reproductive and developmentalimpairments in a wide spectrum of organisms (Chernoff 1973; Manson andO’Flaherty 1978; Rombough and Garside 1982; Pérez-Coll et al. 1985; Belmonteet al. 1989; Rivera et al. 1990). Within the life cycle of organisms, the embryo isthe most sensitive period to adverse conditions (Olsson et al. 1990; EPA 1991).Moreover, stage-dependent susceptibilities to toxic agents in amphibian embryostreated with lead (Pérez-Coll and Herkovits 1990) cadmium (Herkovits and Pérez-Coll 1993) and aluminium (Beattie et al. 1992) were described. In the case ofcadmium, this differential sensitivity could be related to changes in the metalaccumulation through development (Herkovits et al. 1991) or in the induction ofdefense mechanisms against cadmium toxicity, such as metallothionein (Mt)synthesis, which seems to be developmentally regulated (Wilkinson and Nemer1987; Olsson et al. 1990). In the case of the toad Bufo arenarum, susceptibility tocadmium seems to follow a biphasic pattern during embryonic development. Fromthe two-cell stage to the neurula stage an increase in susceptibility occurs, whereasfrom the last stage onwards a gradual increase in the resistance against this heavymetal seems to be achieved (Herkovits and Pérez-Coll 1993).From an ecotoxicological perspective, the threshold concentrations of xenobioticsfor very short exposure periods are meaningful for establishing water qualitycriteria and water quality-based toxic-wastes control, while on the other handamphibian embryos could be very useful for performing short-term toxicity tests. Inthis context, it could be of interest to correlate cadmium toxicity and uptakevalues in B. arenarum embryos exposed to short treatments, as in this case from 15to 240 minutes. Considering that the high resistance against cadmium toxicityduring blastula stage seems to be related to a very reduced uptake of this heavymetal in fish (Michibata 1981), as well as in amphibians (Herkovits et al. 1991), wereport in the present study the uptake profile of cadmium at different post-hatchingstages from the appearance of cardiac beat to the end of embryonic development.Correspondence to: J. Herkovits663