SYNTHESIS REPORT OF THE STEP PROJECT DETECTION OF GERM-CELL MUTAGENS

The project 'Detection of Germ Cell Mutagens' was designed with three major goals: (1) Detection and characterization of germ-cell mutagens; (2) standardization and validation of new germ-cell tests; and (3) de velopment of a data base on germ-cell mutagenicity. All three goals we re achieved, The classical germ-cell tests were applied to characteriz e the genetic effects of acrylamide (AA), 1,3-butadiene (ED), trophosp hamide (TP) and urethane (UR), All but UR were found to cause heritabl e genetic damage. The experimental data obtained for AA and ED were th e basis for genetic risk evaluations during the EC/US Workshop on Risk Assessment 'Human Genetic Risk from Exposure to Chemicals, Focusing o n the Feasibility of the Parallelogram Approach'. Nine chemicals were employed to validate the spermatid micronucleus assay with mice and ra ts: AA, ED and its metabolites 1,2-epoxybutene-3 and 1,2:3,4-diepoxybu tane, chlorambucil, mitomycin C, methylnitrosourea, TP and UR. The spe rmatid micronucleus test was combined with micronucleus tests in somat ic cells such as bone marrow or peripheral blood erythrocytes, and spl enocytes which allowed a comparison of effects in somatic and germinal cells, Improvements of the spermatid micronucleus test included BrdU- labelling of premeiotic S-phase for the determination of stage sensiti vity and fluorescence in situ hybridization with pancentromeric DNA-pr obes to distinguish between clastogenic and aneugenic events. The resu lts indicate that the spermatid micronucleus test with its improvement s is an adequate procedure to detect germ-cell clastogenicity and to c ompare the activity of chemicals in different tissues and between spec ies, i.e., rats and mice, Other germ cell methods under study were the flow cytometric measurement of testicular sperm DNA and the cytogenet ic analysis of preimplantation embryos for chromosomal aberrations and micronuclei. The collection of a reliable germ-cell data base was acc omplished through a critical evaluation of the literature and with the data obtained in the present project. Remarkable concordance between responses of germ cell tests to chemical mutagens was the most strikin g conclusion to be drawn from the present data base.