The Effect of a Single 2,000 R Exposure of X rays upon the Uptake of35S by Soft Tissues of the Mouse Hind Limb

The effect of a single 2,000 R exposure of 200 kVp X rays upon the 35S uptake by the soft tissues of the mouse hind limb was examined throughout a period of up to 23 weeks following irradiation. The normal 35S uptake by the soft tissues falls off with time via three components of half-lives three quarters of an hour, five hours and 60 hours respectively. The effects produced by the irradiation upon the first component are relatively small. It is possible, however, that the irradiation produces two slight waves of uptake depression and elevation during the first 14 weeks after irradiation and then the uptake remains at a slightly depressed (80 per cent of normal) value from 14 to 23 weeks after irradiation. Irradiation effects are most marked in the second component of isotope loss. In this case, after a small, possibly not significant fall produced during the first four to five weeks after irradiation, the 35S uptake rises continuously to more than three times the normal level at about 15 weeks after irradiation. The uptake then falls slowly but is still more than twice normal 23 weeks after irradiation. Effects produced in the third component are very small and may not be significant. Certainly little or no effect is produced during the first seven weeks after irradiation. A very slight rise of 35S uptake (about 20 per cent) may have occurred by nine or ten weeks post-irradiation and this may be followed by a slow steady fall to about 80 per cent of normal uptake at 23 weeks post-irradiation. The use of the effect upon the second component is discussed in relation to possible future studies concerning the effect of age of animal, total dose given, dose fractionation, etc. The possible significance of the results and their relation to those found for the mouse knee joint are also discussed and it is suggested that quantitative biochemical studies of the tissue mucopolysaccharides following irradiation of the tissue would be of value.