SISTER CHROMATID EXCHANGES INVIVO IN CHINESE-HAMSTER EMBRYONIC LIVER-CELLS EXPOSED TRANSPLACENTALLY TO BRDU

The SCE test is typically much more sensitive than the induction of chromosome aberrations, as a significant increase of SCEs can be observed with concentrations much lower than those necessary to induce chromosome aberrations. The method described here may prove useful for investigating whether subtoxic or therapeutical doses of drugs or their metabolites pass the placental barrier and affect embryonic cells. The present baseline values of three to four SCEs per cell in the bone marrow of Chinese hamsters are comparable to those reported in previous studies, in which BrdU was injected. Cultivation of bone marrow cells for 2 h, as well as implantation of a BrdU tablet instead of repeated BrdU injections, did not seem to influence the SCE frequency. Allen et al. (1978), however, reported that SCE frequencies in mice were generally higher in animals receiving BrdU injections. It remains to be determined whether this reported high baseline SCE frequency of 6.1 in Chinese hamster bone marrow cells was due, for instance, to the use of ether as an anesthetic for implanting the tablet or to different BrdU tablets.