Post-exposure phenomen in murine lymphoma L5178Y-S cell populations grown in media containing tritiated compounds.

Murine leukaemic lymphoblasts L5178Y-S were exposed to: (a) 104 muCi of 3HOH for time intervals from 25 to 600 h, (b) 10 muCi of L-[4,5(n)-3H] lysine for 25 to 600 h, and (c) 0.05 muCi of [methyl-3H]thymidine for 4 to 600 h. Extended post-exposure observations of growth disturbances and viability changes indicate marked differences between heritable lesions induced by the three tritiated compounds. After exposures to tritiated lysine and tritiated water, the damage was predominantly of non-lethal character while in the populations previously exposed to tritiated thymidine most of the cells eliminated during the post-exposure growth were lethally damaged. In all cases examined growth retardation was observed followed by growth at the normal rate. An exception concerned a cell culture exposed for 600 h to tritiated thymidine for which the slowed-down growth was observed for ca seventy cell generations.