Inducibility of somatic colour and white spots in the mammalian spot test.

F1 embryos of the C57BL/6JHan x T-Stock were exposed to utero to 5, 10, 15 and 45 mg/kg b.w. of cyclophosphamide (CP) s.c. on the 10th day of pregnancy. 3-5 weeks post-partum the offspring were examined for the appearance of recessive coat-colour mosaics and white midventral spots (WMVS). The frequencies of the coloured spots were 0.93 and 2.59% at 5- and 10-mg/kg doses of CP, resp. These frequencies were dose-dependent, but the difference between the doses was not significant. No coloured spots were obtained with CP at 15 and 45 mg/kg. The frequencies of WMVS were much higher than those of coloured spots (1.40, 6.03 and 51.16%, resp.). The differences were highly significant. The reduction in the number of offspring compared with the raio of the offspring/female of the control (control = 100%) were 16.16, 22.72, 72.48 and 100% at the different doses of CP (5, 10, 15 and 45 mg/kg b.w.).