Cellular responses to Cd, Pb and Zn in shrews (Myosorex varius and Crocidura flavescens) and BALB/c mice

[摘要] ENGLISH ABSTRACT:Shrews are excellent bioindicators of environmental heavy metal pollution. This isdue to their diets and the high rate of consumption at which these small mammals consumetheir prey. Shrews feed mostly on earthworms, and earthworms accumulate high levels ofheavy metals in their bodies. Biomarkers measure responses to environmental pollution in thebodies of exposed organisms. Cellular biomarkers give an indication of responses topollutants at levels of pollutant exposure that are not yet lethal to the organism.This study was prompted by concern that the number of shrews in the Stellenboschregion was declining. For the present study, shrews (Myosorex varius and Crocidurajlavescens) from the Stellenbosch region were sampled. The levels of Cd and Pb in theirbodies were analysed in order to ascertain whether or not these two heavy metals, whichoccur in the environment as a result of various anthropogenic activities, are present in thefood chain of the shrews. In the laboratory, shrews were fed live control and metal exposedearthworms from laboratory cultures. The earthworms had been exposed to either Cd or Pb inthese cultures over a number of generations. This was performed to determine whether thepresence of the metals in the body of the shrews, had resulted from metal accumulation fromthe earthworms which were fed to the shrews. Cellular biomarkers were used to determinethe cellular response to the metals and membrane integrity and DNA integrity wereinvestigated. This was done by exposing the cells of the shrews and ofBALB/c mice to metalsalt solutions of Cd, Pb and Zn in vitro. Membrane integrity was tested by cell leachingtechniques viz. the LDH assay and the trypan blue assay. DNA integrity was determined byusing the comet assay as a biomarker of exposure.The results of the study show that the shrews in the immediate Stellenbosch region areexposed to lower levels of Cd and even lower levels of Pb than shrews from a site 16km outof the town of Stellenbosch. The cellular responses induced by metal exposure of laboratorymice show that the metals are indeed cytotoxic and genotoxic to the cells of small mammals.Cd and Pb were found to be more cytotoxic than Zn, while Zn was more genotoxic than eitherCqorPb.

[发布机构] Stellenbosch University