Effect of age at treatment on the incidence and location of neurogenic tumors induced in Wistar rats by a single dose of N-ethyl-N-nitrosourea.

The effect of age at treatment on the incidence and location of neurogenic tumors induced by N-ethyl-N-nitrosourea (ENU) was investigated in 232 Wistar rats of both sexes. Rats were given 40 ng/kg of ENU on the 16th day of gestation (group I), on the day of birth (group II), and on the 1st week (group III), 2nd week (group IV), 3rd week (group V) and 4th week (group VI) after birth. Up to 6 months of observation, the brain consistently showed the highest susceptibility ranging from group I (93%) to group VI (36%), followed by the spinal cord (group I, 34%; group II, 64%; group III, 43%). However, the trigeminal nerve was only susceptible in group I (27%) and group II (36%) and the spinal root was susceptible exclusively in group II (46%). Most of the tumors obtained were oligodendrogliomas or mixed gliomas. Glioependymomas of the spinal cord were predominant only in group II. The temporal and paraventricular regions and hippocampus were the preferred sites of brain tumors in group I and II, but in groups III and IV frontal tumors were predominant. Mesenchymal tumors of the kidney were also induced, mainly in groups III (16%) and IV (16%).