The effect of doses of mixed gamma-neutron radiations or 14-MeV neutrons on the urinary excretion of deoxypyrimidines calculated as deoxycytidine equivalent (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 equivalent in the urine of irradiated rats during the 4- to 12-hour postirradiation interval was a function of dose over the range of 22-376 rads. The response was similar for the different types of radiations. In a group of 10 rats exposed to the same does of x-rays (50, 150, or 450 rads) on 3 successive days, the 4- to 12-hour postirradiation excretion of CdR equivalent was dose dependent after the initial exposure but not after the second and third exposures. The total CdR equivalent excretion after an accumulated dose of 150-1350 rads approximated that of an equal single dose. The disappearance of circulating lymphocytes paralleled the urinary excretion of CdR equivalent. After lymphocytes had essentially disappeared following two 450-rad doses of x-rays, a third dose of 450 rads induced less excretion of CdR equivalent by irradiated rats than by unirradiated control animals. Calculations of the amount of CdR equivalent excreted per deleted circulating lymphocyte suggest that there are other radiosensitive cells that contribute to deoxypyrimidinuria.

Fluorescence intensity of serum and urine in rats exposed to mixed gamma-neutron radiations was evaluated for dose-dependent changes. Male Sprague-Dawley rats were exposed to doses in the range from 570 to 30,000 rads. Sera and urines were collected 6, 12, 24, 48, and 72 hours after exposure. Emission spectra of diluted sera and urines were measured with a spectrophotofluorometer, and two peaks in the emission spectra of each were studied. A maximal change in fluorescence intensity of sera at 465 nm with exciting light at 350 nm occurred 24 hours after irradiation. The fluorescence intensity decreased with dose in the range from 570 to 9300 rads. An increase in fluorescence intensity at 360 nm (exciting light, 295 nm) occurred 72 hours after doses of 4700 or 9100 rads, but it was not shown to be dose-dependent. In urine, the fluorescence intensity at 425 nm (exciting light, 345 nm) increased as a function of dose in the range from 1000 to 30,000 rads. The intensity at 400 nm (exciting light, 295) did not change with dose. The results indicate that the changes in fluorescence intensities of sera at 465 nm and of urines at 425 nm from irradiated rats show limited usefulness as biological dosimeters.