NO INDICATIONS OF AN ENHANCED UV-LIGHT INDUCED UNSCHEDULED DNA-SYNTHESIS IN SPLENOCYTES OF MICE FOLLOWING A LOW-DOSE IRRADIATION IN-VIVO ORIN-VITRO

One of the open questions regarding the adaptive response to ionizing radiation it; whether it can be induced in G(0) lymphocytes. In the ma jority of experiments in which an adaptive response in G(0) lymphocyte s was observed, the adapting dose was applied in vivo. In order to inv estigate whether there is some in vivo component of adaptive response, mouse splenocytes of the C57BL/6 strain were irradiated with 0.1 Gy x -rays either in vivo or in vitro, and their UV-light-induced unschedul ed DNA synthesis (UDS) levels were determined autoradiographically. An augmented UV-light-induced UDS following an adapting dose applied in vivo has previously been described by several authors in splenocytes o f C57BL/6 mice, indicating that the adapting dose enhanced the DNA rep air capacity of lymphocytes. In the present investigation, however, no evidence of an adaptive response could be seen regardless of whether the adapting dose was given in vivo or in vitro. Those results present a further indication for the fact that the adaptive response to ioniz ing radiation is not always inducible, even in lymphocytes of an inbre d mouse strain in which its existence has been reported before.