The Effects of X-irradiation on the Biosynthesis of Haemoglobin

1. The degree of incorporation of PBG-3,5-14C into haemin was determined in bone-marrow homogenates of rabbits after 600 r, 800 r or 1000 r of whole-body x-irradiation.2. The time-periods studied after exposure to x-rays ranged from 30 min to 48 days.3. In parallel with the capacity of bone-marrow to synthesize haemin, DNA-concentration and haemin-concentration were determined.4. The capacity of bone-marrow homogenate to synthesize haemin increased significantly on the first, seventh and fourteenth day after exposure to 600 r and on the seventh and fourteenth day after exposure to 800 or 1000 r.5. After exposure to 800 r, similar patterns of radiation-induced changes were found when PBG or DAL were used as precursors. These patterns differed markedly from those observed when glycine was used as a precursor.