SOME EFFECTS OF 138 MEV PROTONS ON PRIMATES. THE RADIATIONS OF SPACE III

One hundred two primates Macaca mulatta were irradiated with spaced doses of 138 Mev protons ranging from 105 to 1,220 rads. An LD5030 of 516 plus or minus 30 rads was estimated from the cumulative mortality data. A comparison of the proton LD5030 with the LD5030 from a previous study in which primates were irradiated with 2 Mev x-rays provides an estimate of 1.30 plus or minus .09 S.E. for the mortality RBE. Adjusting the 2 Mev x-ray LD5030 to correspond to the 138 Mev proton dose rate gives an RBE of 1.04. Changes in total leukocyte count, lymphocyte count, neutrophil count, platelet count, hemoglobin concentration, hematocrits, LDH concentrations, and SGOT concentrations indicate an RBE of 1 for 138 Mev protons as compared to 2 Mev x-rays. The only findings which were significantly different between these qualities of radiation were clinical. Considerably more pronounced signs of gastrointestinal injury and hemorrhage were produced by 138 Mev protons as compared to equivalent doses of 2 Mev x-rays.