[Transplacental blastomogenic effect of N-nitrosomethylurea in rats with constant estrus].

As a result of transplacental exposure of rats of NMU in the dosage of 20 mg/Kg (intraperitoneally) on the 21st day of pregnancy tumors in the offspring developed in 6 to 16 females and in 10 of 17 males. In rats with persistent estrus, induced in sex mature females by their castration and one-moment autoimplantation of ovaries in the tail, tumour developed in 25 of 41 animals. In combination of transplacental effect of NMU and postnatal induction of persistent estrus in females neoplasms were recorded in 14 of 17 animals, the incidence of neoplasms of the nervous system and kidney observed only after transplacental NMU exposure of males being increased. Hormonalmetabolic shifts observed in rats with persistent estrus seemed to potentiate transplacental blastomogenic action of NMU.