Residual Radiation Injury: Hematopoietic and Gastrointestinal Involvement in Relation to Age

Abstract

Residual radiation injury (the depression in resistance to 140 R/day, 5 days a week) owed to 500 R given 30 days earlier has been measured in C57BL/6J female mice between the ages of 3 and 23 months. Control mice (previously unirradiated) demonstrate a parabolic relationship between age and resistance to this exposure regimen, whereas preirradiated (500 R) mice demonstrate resistance levels which are inversely related to age. The state of the bone marrow, in terms of endogenous colony-forming unit patterns, in previously unirradiated aging mice correlates with their resistance to fractionated exposures, but it does not predict the inverse age-resistance relationship in aging mice given 500 R 30 days earlier. Bone marrow transplantation immediately after a lethal dose of x-rays reduces the residual injury detectable in young adult mice which survive for 30 days but does not remove the age-dependence for residual injury induction. Shielding of the trunk during exposure allows the residual injury measured 30...