Increase during passage in culture in susceptibility of Syrian hamster embryonic cells to induction of chromosome aberrations by 7,12-dimethylbenz(a)-anthracene.

Studies were made on chromosome aberrations in Syrian hamster embryonal fibroblasts (SHEF) at early and late passages in culture. Aberrations were induced with a potent indirect clastogen, 7,12-dimethylbenz(a)anthracene (DMBA). Results showed that cells at late passages were much more susceptible to this chemical than cells at early passages: the frequency of aberrant metaphases was usually less than 20% at the 2nd passage, but it gradually increased with increase in the number of culture passages, reaching 50% or more at the 8th passage in one experiment and 6th-7th passage in another. Induction of chromosome aberrations was also examined in V79 cells co-cultured with hamster cells at early and late passages. V79 cells are known to have no drug-metabolizing enzyme activity. Results demonstrate that the frequency of chromosome aberrations of V79 cells was much greater in the presence of hamster cells at late passages than in the presence of cells at early passages.