EARLY SKIN SHRINKAGE, LATE SKIN CONTRACTIONAND LEG CONTRACTURE OF MICE EXPOSED TO TWO EQUAL FRACTIONS OF NEUTRON

Abstract

We evaluated the effects of fractioned intervals on normal tissue recovery from radiation injury after neutron exposure. Doses ranging from 9 to 25 Gy of 30 MeV deuteronberyllium neutrons (0.7Gy/min.) were imposed on the hind legs of C3H/He female mice in single or in two equally divided doses at various intervals ranging from 6 hours to 14 days. The effective doses 50% for early skin shrinkage measured at around 40 to 50 days, late skin contraction and leg contracture at 250 days after irradiation were evaluated. With recovery ratios, (D2-D 1)/D 1, the patterns obtained were similar to those observed in the isoeffect curves. However, with one or two day intervals, they remarkably decreased to less than 10% irrespective of the response evaluated especially in late skin contraction. This might indicate the induction of hypersensitivity and/or very little recovery at these intervals. Therefore, fractioned intervals of more than five days and around one and/or two days seem less beneficial from the view point of normal tissue recovery.