Increase in Endogenous Spleen Colonies without Recovery of Blood Cell Counts in Radioadaptive Survival Response in C57BL/6 Mice

Abstract

The radioadaptive survival response induced by a conditioning exposure to 0.45 Gy and measured as an increase in 30-day survival after mid-lethal X irradiation was studied in C57BL/6N mice. The acquired radioresistance appeared on day 9 after the conditioning exposure, reached a maximum on days 12-14, and disappeared on day 21. The conditioning exposure 14 days prior to the challenge exposure increased the number of endogenous spleen colonies (CFU-S) on days 12-13 after the exposure to 5 Gy. On day 12 after irradiation, the conditioning exposure also increased the number of endogenous CFU-S to about five times that seen in animals exposed to 4.25-6.75 Gy without preirradiation. The effect of the interval between the preirradiation and the challenge irradiation on the increase in endogenous CFU-S was also examined. A significant increase in endogenous CFU-S was observed when the interval was 14 days, but not 9 days. This result corresponded to the increase in survival observed on day 14 after the challenge irradiation. Radiation-inducted resistance to radiation-induced lethality in mice appears to be closely related to the marked recovery of endogenous CFU-S in the surviving hematopoietic stem cells that acquired radioresistance by preirradiation. Preirradiation enhanced the recovery of the numbers of erythrocytes, leukocytes and thrombocytes very slightly in mice exposed to a sublethal dose of 5 Gy, a dose that does not cause bone marrow death. There appears to be no correlation between the marked increase in endogenous CFU-S and the slight increase or no increase in peripheral blood cells induced by the radioadaptive response. The possible contribution by some factor, such as Il4 or Il11, that has been reported to protect irradiated animals without stimulating hematopoiesis is discussed.

Gamma-tocopherol-N,N-dimethylglycine ester as a potent post-irradiation mitigator against whole body X-irradiation-induced bone marrow death in mice

“…The number of endogenous spleen colonies formed after X-irradiation was measured as reported previously [39]. Mice (five per group) were administered i.p.…”

Life span alteration after irradiation in Drosophila melanogaster strains with mutations of Hsf and Hsps

“…However, it is necessary to investigate whether these effects have common molecularcellular pathways. Unfortunately, only few groups demonstrated radioadaptive survival responses (Yonezawa et al 1990(Yonezawa et al , 1996(Yonezawa et al , 2004Nose et al 2001;Ito et al 2007). All previous works were prepared on mice and the results were explained by hematopoietic stem cells excitation.…”

Induction of adaptive response: Pre-exposure of mice to 900 MHz radiofrequency fields reduces hematopoietic damage caused by subsequent exposure to ionising radiation

“…Int J Radiat Biol Downloaded from informahealthcare.com by Serials Unit -Library on 10/07/12 both of them are derived from a single hematopoietic stem/progenitor cell (Yonezawa et al 2004). These observations indicated increased stimulation/proliferation of hematopoietic stem cells.…”