PRIMORDIAL GERM CELL-DERIVED EMBRYONIC GERM-CELLS OF THE MOUSE - IN-VITRO MODEL FOR CYTOTOXICITY STUDIES WITH CHEMICAL MUTAGENS

Different screening methods to detect the toxic effects of xenobiotics using cells from vertebrates and invertebrates in cytotoxicity and vi ability assays have been developed, but up to now appropriate in vitro methods with mammalian germ cells have not been available. In the pre sent study the primordial germ (PG) cell-derived permanent embryonic g erm (EG) cell line EG-1 was used as in vitro model in toxicity studies with chemical mutagens. EG-1 cells and embryonic stem cells of line D 3 were comparatively investigated for their cell survival in response to N-ethyl-N-nitrosourea (ENU), N-methyl-N'-nitro-N-nitrosoguanidine ( MNNG) and mitomycin C (MMC) and the results compared with those obtain ed for undifferentiated embryonic carcinoma cells of line P19 and diff erentiated epithelioid EPI-7 cells. As a prerequisite for in vitro tox icity and viability studies the cultivation conditions for EG-1 and D3 cells in the absence of a feeder layer were improved by a conditioned medium, increasing the plating efficiency from 0.08% to 17.5% and fro m 21.1% to 25.1% for EG-1 and D3 cells, respectively. The resulting me an generation time (MGT) of 16.9 hr for EG-1 cells was identical to th e generation time of PG cells in vivo, and was not significantly diffe rent from the MGT of D3 (15.6 hr) and EPI-7 (13.7 hr) cells, but signi ficantly longer than the MGT of P19 cells (9.3 hr). Calculations of th e concentrations resulting in vitro in a 50% decrease in cell survival demonstrated that EG-1 cells were more sensitive to the toxic effects of ENU, MNNG and MMC than D3 and P19 cells and, with the exception of MNNG, also more sensitive than EPI-7 cells. It is proposed that EG ce lls are used as a model system to screen for toxic effects of teratoge nic and embryotoxic chemical agents in vitro. (C) 1997 Elsevier Scienc e Ltd.