[The role of the hemopoietic microenvironment on the hemopoiesis-stimulating effect of cystamine].

The influence of cystamine delivered in a radioprotective dose before and after irradiation of mouse-recipients (8 Gy) on the effectiveness of exogenous bone marrow cloning has been investigated. Cystamine administered prior to irradiation exerts a protective effect on CFUs and also causes an increase in the number of splenic colonies grown from CFUs of the transplanted bone marrow. With cystamine administered after irradiation the protective effect is absent, but the CFUs number in the femur increases in recipients transplanted with intact bone marrow in comparison with those transplanted without cystamine. It is believed, that in addition to the specific protective mechanism of action of radioprotectors, there is a nonspecific mechanism of increasing the proliferation of protected stem cells that is connected with the stimulatory effect of radioprotective agents on the haemopoietic stroma elements.