[Changes of protein metabolism after X-irradiation. III. Dose dependent changes of the protease activity, the protein and the free amino acids in the spleen, liver, blood plasma, erythrocytes, stomach- and intestinal wall and in the carcass of rats after whole body X-irradiation with 400-1000 R (author's transl)].

The protease activity against externally added haemoglobin as a substrate and the autolytic activity against the proteins of the organism were decreases in most of the organs and in the total organism on the 3rd day after irradiation. This contradicts the explanation of the protein loss by an increased protein degradation. The free amino acids in the organs and in the whole organisms are unchanged or diminished. An increase would be expected if an increased protein degradation had occured because the free amino acids are the end product of the protein degradation. The conclusion of this investigation is that other mechanisms than protein degradation are responsible for the protein loss of the organism 3-6 days after X-irradiation. The increase of the protease activity and of the free amino acids in the blood plasma from day 1-3 coincides with the end of the destruction phase in the organism between day 1-2 after irradiation. The changes of the protease activity in the erythrocytes between day 1-30 after irradiation are probably not caused by a direct effect of the radaition on the erythrocytes of the peripheral blood. They are rather the results of a transient suppression of the hematopoeitic differentiation.