Neuronal degeneration caused by ethylenethiourea in neuronal monocell layers in vitro and in fetal rat brain in vivo.

The monocell layers, containing a mixture of neuronal and non-neuronal (primarily glial) cells, were obtained by growing cells dissociated from trypsinized fetal brains of 19-day pregnant rats under optimum conditions. Ethylenethiourea (ETU), at greater than or equal to .5 mM concentrations, caused in monocell layers in vitro a necrosis of neuronal cells and a marked depression in the formation of neurites and fascicles without any noticeable change in the non-neuronal cells. In the in vivo study, ETU orally administered as a single 30 or 45 mg/kg dose to rats on day 19 of pregnancy was found to induce necrosis of neuroblasts in the fetal CNS after 18 and 24 hours of dosing and a high incidence of hydrocephalus in postnatal pups at both doses. In an in vivo/in vitro experiment, rat fetal brains from 19-day pregnant dams which had previously been dosed with 80 or 120 mg ETU/kg were trypsinized and then dissociated into a cell suspension in a nutrient medium. The total number of viable cells in the suspension was significantly reduced compared to the number in the control suspension. The test suspension with cell density adjusted to that in the control suspension grew into monocell layers manifesting a marked decreased population of neuronal cells with a concomitantly increased population of non-neuronal cells. It was concluded that the target of ETU action was most likely the neuronal cells rather than the organization of nervous tissue per se.