Effects of single dose and fractionated irradiation on foetal mouse brain aggregates

Foetal mouse brain cells were grown in vitro. 1 Gy X-irradiation was given as a single dose on culture day 2 (corresponding to embryonic day 17 in vivo) or in daily fractions (4 x 0.25 Gy), starting on day 2 in culture. The growth (size) and biochemical differentiation of the aggregates were studied up to day 40 in culture. Aggregates given a single dose (1 Gy) were smaller with lower protein and DNA amount than controls up to day 30-40 in culture. When the dose was fractionated, a partial recovery occurred by day 20, and values returned to control levels by day 30-40. The specific activity of acetylcholinesterase (AChE) was significantly higher after 10-20 days, in the irradiated (1 Gy) aggregates. In fractionated irradiated aggregates, the increase of specific activity of AChE was evident only after 10 days in culture. Compared with fractionated X-irradiation, where recovery was observed after 20-40 days in culture, a single dose of irradiation produced more permanent changes in the amounts of DNA and protein and in the size and neurochemical activities of aggregates.