The induction of the Trp53 response after very low doses (0.01-1 Gy) of ion
izing radiation was studied in the adult mouse using immunochemical and imm
unohistochemical methods. We found a detectable response at 0.01 Gy and an
increased induction of Trp53 with increasing dose in both radiation-resista
nt and radiation-sensitive tissues. These results suggest that there is no
lower threshold for induction. This response was heterogeneous, since cells
that received the same dose had different staining intensities, suggesting
that the induction of Trp53 is not based simply on dose-dependent response
s to DNA damage. These data also demonstrate the exquisite sensitivity of t
he Trp53 pathway and show that this response is controlled by cell- and tis
sue-specific factors that have yet to be defined. (C) 2001 by Radiation Res
earch Society.