Hematologic Changes in Rats Protected from Lethal X-Radiation by Post-Irradiation Parabiosis

Abstract

Since its introduction by Brecher and Cronkite (1), post-irradiation parabiosis has served as a satisfactory means of protection of experimental animals from lethal amounts of X-radiation. The mechanism of this protection has remained obscure, however. The state of parabiosis is characterized by a relatively large exchange of blood between the two partners (2), and it is thought that this exchange may transmit the protective factors. The importance of the hemapoietic system in protection from irradiation damage has been indicated by other methods, such as spleen or bone marrow shielding (3, 4) or injection of spleen or bone marrow homogenates (5, 6). Previous pre-irradiation parabiosis studies have demonstrated exchange of leucocytes and erythrocytes and have shown that the damage to the parabiont is not as severe as that of the single animal, presumably owing to the cross circulation (7, 8). It is the purpose of the present experiment to investigate the hematologic aspects of post-irradiation parabiosis, i.e., surgical union after X-radiation, in an attempt to elucidate the role of circulating blood in protection from radiation injury.