A model in comparative teratogenesis, dose response to 5-fluoro-2- -deoxycytidine (fcdr, ro 5-1090) in organogenesis of mice of strains c57bl/6jhanffm and c57bl/10jffm.

The toxic and teratogenic dose-response relations of 5-fluoro-2-deoxycytidine (FCdR) were tested in strain C57BL/6JHanFfm at stage VIII of pregnancy, in substrain C57BL/10JFfm-+ld at stage IX, and in strain C57BL/10JFfm at stage XI. Attention was focused on three regions of the skeletal system: skull, vertebral column, and limbs. The nonteratogenic range was nearly the same in all groups; differences were due only to the broadness of teratogenic range. This range was rather narrow at stage VIII in strain C57BL/6JHanFfm and quite broad at stage XI in strain C57BL/10JFfm. Concerning teratogenicity, at stage VIII in strain C57BL/6JHanFfm there was a high amount of single regional defects in the vertebral column (VC) and multiple regional defects (m.r.d.) in the skull and VC; at stage IX in substrain C57BL/10JFfm-+ld there was again a high rate of single regional defects in the VC, which were substituted by m.r.d. in all three parts of skeleton at higher doses of FCdR. At stage XI in strain C57BL/10JFfm the teratogenic effects started with single regional defects in the VC and continued with m.r.d. in VC and limbs; at the highest dose (20 mg/kg) it changed to m.r.d. of the three main regions of skeletal system.