Spinal cord tumors induced by N-ethyl-N-nitrosourea in rats: presence of spinal subpial target cells.

The correlation between induction of spinal cord tumor by N-ethyl-N-nitrosourea (ENU) (CAS: 759-73-9; 1-ethyl-1-nitrosourea) and postnatal cellular differentiation of the spinal cord was examined in 6 different strains of rats [noninbred Wistar and inbred F344, WF, LE, WF (female) X LE (male), and LE (female) X WF (male)]. By perinatal injection of 40 mg ENU/kg, 258 spinal cord tumors were induced in 175 of 372 ENU-treated rats. The spinal cords of rats at ages ranging from day 1 to day 8 after birth were particularly susceptible to the oncogenic effect of ENU. All spinal cord tumors developed in the white matter without any segmental predilection site. Moreover, most (93%) were found in the subpial region of the spinal cord and were classified as oligodendrogliomas. Morphologic and autoradiographic examinations revealed accumulation of spinal subpial immature glial cells from day 1 to day 8 after birth when the spinal cord had a high susceptibility and most of the cells were destined to differentiate into oligodendrocytes. These data show the existence of target cells in the spinal cords of rats after ENU carcinogenesis.