trabecular bone changes induced by fast neutrons versus gamma rays in mice

background: the trabecular bone changes in the tibia of c3h/hen mice were measured 12 weeks after whole body irradiation with various doses of fast neutrons (0-2.4 gy) or 137cs-generated gamma-rays (0-6 gy). materials and methods: serum calcium, phosphorus, estradiol concentration and alkaline phosphatase activity were measured. tibiae were analyzed using microcomputed tomography. biomechanical property and osteoclast surface level were measured. results: there was a significant relationship between the loss of bone architecture and the radiation dose, and the best-fitting dose-response curves were linear-quadratic. mean relative biological effectiveness (rbe) values (ref. gamma) of 2.05 and 2.33 were estimated for fast neutron irradiation in trabecular bone volume fraction and bone mineral density, respectively. there was a substantial reduction in osteoclast surface level in tartrate-resistant acid phosphatase-stained histological sections of tibial metaphyses in irradiated mice with high dose of neutrons. conclusion: there was a significant relationship between the loss of bone architecture and the radiation dose. the difference of osteoclastic bone resorption may represent a contributor to the low rbe in high dose of irradiation level relative to that of low dose level.