The Effect of X-Rays of Different Qualities on The Alkaline Phosphatase of Living Mouse Bone: II. Effects of 22.5-Mevp X-Rays

Abstract

The purpose of this work is to extend previous observations on the correlation between loss of alkaline phosphatase and absorption of energy in irradiated mouse bone so as to include the effects of 22.5-Mevp X-rays produced by the betatron. Bone has a higher concentration of phosphorus and an enormously greater concentration of calcium than other living tissues, and thus has a greater effective atomic number than soft tissue, air, or water. Physical measurements have shown (1) that the linear absorption coefficient in human cortical bone of X-rays of a wavelength of 0.45 A exceeds that in muscle by a factor of about 7. Much of this energy is dissipated in the crystalline calcium salts in the bone and cannot be expected to have an appreciable biological effect, but some of the secondary radiation produced in the bone salts may be expected to damage near-by soft tissue. The amount of such secondary radiation which would be absorbed by soft tissue masses embedded in, or adjacent to, dense bone has been calculated by Spiers (2) and by Wilson (3). To obtain a satisfactory correlation between energy absorbed and resultant biological damage, it is necessary to measure some metabolic process in bone with a precision comparable to that obtainable in the measurement of energy absorption. In a previous paper (4) Woodard and Spiers described a method in which the midportion of one hind leg of each of a series of mice was irradiated, and the alkaline phosphatase activity of the irradiated bones was compared with that of the contralateral control bones of the same animals at various times after treatment. This method has the advantage that the phosphatase measurements can be made with satisfactory precision, and that the approximate size of the phosphatase-producing