Increased protective effect of cystamine and mexamine against radiation after activation of the haemopoiesis by dextran sulphate in mice.

The effect gained by activation of haemopoietic cell populations by a single injection of dextran sulphate (DS) on the protective effect of cystamine and mexamine administered in small doses was monitored in mice. On irradiation 24 hours after the injection of DS the number of endogenous spleen colonies increased following the administration of mexamine and cystamine, the number of haemopoietic stem cells surviving in the femur after irradiation increased, and recovery of the cellularity of irradiated bone marrow was accelerated. Both substances administered 24 hours after the injection of DS significantly reduced the lethal effects of gamma rays. The maximum values of the dose reduction factor, for combined radiation protection, reached 1.48 as regards decreased lethal effects and 1.6 as regards equieffective E-MSC exposure.