Rate of Recovery from Radiation Damage and Its Possible Relationship to Life Shortening in Mice

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Abstract
Data from a number of published reports on the survival times of mice exposed to daily doses of radiation were examined and mean recovery rate constants for animals exposed to different numbers of doses were calculated. The mean rate at which mice recover from the radiation damage contributing to acute death can be related empirically to the number of daily radiation doses delivered. Recovery from neutron-induced damage is slower at all time intervals than recovery from X or gamma-radiation damage. By using the empirically derived relationships and certain assumptions about the change in LD50 with age, it was possible to predict the general form of the relation between daily dose and shortening of life span. Application of the equations to the problem of increased sensitivity to further exposure following various regimens of small daily doses is discussed. A consequence of the derived equations is that the relative lethal effectiveness of neutrons varies with the size of the daily exposure. A hypothesis relating recovery rate to life shortening in general is advanced.