Deoxypyrimidinuria and lymphocytopenia as indicators of absorbed radiation dose in rats.

The effect of doses of mixed gamma-neutron radiations or 14 MeV neutrons on the urinary excretion of deoxycytidine (CdR) was evaluated as a biodosimeter in rats. The rats were exposed to doses in the range from 22 to 780 rads. The excretion of CdR in the urine of irradiated rats during the 4to 12-hour postirradiation interval was a function of dose over the range of 22 to 376 radsThis response was similar for the different types of radiations. In a group of 10 rats exposed to the same dose of x rays (50, 150, or 450 rads) on three successive days, the 4to 12-hour postirradiation excretion of CdR was dose dependent after the initial exposure but not after the second and third exposures. The total CdR excretion after an accumulated dose of 150 to 1350 rads approximated that of an equal single dose. The disappearance of circulating lymphocytes paralleled the urinary excretion of CdR. After lymphocytes had essentially disappeared foilowing two 450-rad doses of x rays, a third dose of 450 rads induced less excretion of CdR by irradiated rats than by unirradiated control animals. Calculations of the amount of CdR excreted per deleted circulating lymphocyte suggest that there are other radiosensitive cells that contribute to deoxycytidinuria.