Lead levels in bone and hair of rats treated with lead acetate

Book of Abstmcts - EUROTOX ‘94 Application of the Benchmark Method to Ttlchloroethene Toxtclty Data M. Haag-GriZrnlund. R. Fransson-Steen.K. Victorin. institute of Environmental Medicine, Rrolinska Institute, Stockholm, Sweden An alternative approach for risk assessment of non-genotoxicsubstances, the benchmark method, has been evaluated and applied to trichloroetheneas a test case. The benchmark dose is the dose that, based on the dose-response curve. corresponds to a specific increase in risk, normally 1% or 10%. Experimental data from the literature on trichloroethene were used for these calculations. Eighty sets of data on liver-, kidney- and CNS-effects as well as tumours were analysed. All NOELs were higher than the benchmark dose corresponding to 1% extra risk and 42% of the NOELs and 93% of the LOELs were higher than the benchmark dose corresponding to 10% extra risk. The present study confirms that the benchmark methodology gives a more detailed picture of dose-response relationships than in risk assessment using the NOEL/uncertainty factor approach, and facilitates comparisons between different bioassays. However, the polynomial regression models used in the present study quite often failed to fit the experimental data. Despite the theoretical advantages with the benchmark approach, several factors have to be considered in the risk assessment process. In the case of trich!oroerhene. a revised risk assessment using the benchmark approach would lead to a similar guideline value as the traditional NOEL/LOEL approach. Key words: benchmark: LOEL: NOEL; risk assessment; trichloroethene

Lead Levels in Bone and Hair of Rats Treated wlth Lead Acetate Eugeniusz Ha& Jerzv Krechniak. Department of ToxicoloogMedical Academy in GdarZsk,Poland Introduction: Recently hair has been used increasingly as an index of exposure to heavy metals. The aim of this study is the determination of lead levels in bone and hair in the relation to the administrated dose and time of exposure in rats treated orally with lead acetate. Methods: Male albino rats were given for 12-16 weeks tap water containing lead acetate in the following concentrations: 41.7. 83.3 and 166.6 mg Pb/l. Animals receiving the intermediate dose (83.3 mg Pb/lj after 12 weeks of treatment were maintained on tap water for another 9.2 weeks on purpose to study the elimination of lead from bone and hair. During exposure and postexposure period every 4 weeks hair and femur bones were obtained. After preparations and ashing determination of,read was performed on Pve Unicam SP 192 AAS at 283.3 nm with a background correction. Resultsand discussion:In dosed rats the deposition of lead in bone and hair occurred in a dosedependent manner. A relationshipbetween lead levels in bone and hair has a positive correlation (r = 0.876). The regression equation was as follows: ug Pblg bone = 0.842 x ug Pb/g hair + 1.868. After discontinuation of exposure a significant decrease of lead content in both investigated materials was noted. In hair 9.2 weeks after the cessation of exposure the initial lead level was reached. In bone still 64% of the maximal concentration remained at the end of the experiment. Conclusion.The results of this study seem to indicate that during continuous exposure the lead level in hair reflects i. content in bone. When the conditions of exposure are changing the lead content in hair reflects the actual hazard. Key words: lead; hair; bone; rat; indicator of exposure

Highly Experienced Staff and Optimal Conditions Ensure a High Efflclency In the Production of Transgenic Animals A. HBrri. U. Mlrki. Biological Research LaboratoriesLtd., Fiillinsdorl:Switzerland The establishment of newer techniques in the transgenic technology made it possible to induce specific changes in the genom of animal cells. Resulting transgenic animals offer significant utility as models of human and animal diseases and unique opportunityfor investigating immune and metabolic pathways as well as for exploring mechanisms of development, mutagenesis and teratogenesis. The two techniques microinjection and blastocyst injection are currently used for the production of transgenic animals. The injection of the gene construct into one of the pronuclei of fertilized ova and of embryonic stem cells into the blastocoels of the blastocysts can be done successfully within two weeks. The manipulated embryos are transferred under strict aseptic conditions into the high quality SPF recipients. The future trend in toxicity testing will result in tests involving more sophisticated techniques like transgenic technology with the use of specific transgenic animals of a high hygienic quality. Key words: transgenic animals: SPF animals; microinjection; blastocyst injection; embryo transfer