MODIFICATION OF RADIATION INJURY IN RATS THROUGH GASTROINTESTINAL TRACT SHIELDING AND BONE MARROW THERAPY
The efficacy of bone marrow therapy in preventing radiation mortality was compared in rats x-irradiated with three grossly different amounts of intestine surgically exteriorized and lead shielded at the 750 and 800 r dose levels, and with essentially all of the gastroin-testinal tract exteriorized and shielded at doses from 1,000 to 1,400 r. The post-exposure administration of isologous bone marrow failed to enhance survival significantly following 760 to 800 r of whole-body xirradiation, where deaths occurred predominantly during the first post-exposure week from intestinal injury, whereas significant protection was afforded by the marrow treatment in animals irradiated with portions of the intestine shielded. Shielding the gut, regardless of amount, during exposure to 760 to 800 r virtually eliminated the incidence of 3 to 6 day deaths associated with acute intestinal radiation injury. As the amount of intestinal tissue shielded was increased, the total 30day mortality was decreased and the mean survival time of the decedents was increased. When the intestinal component of whole-body radiation syndrome was eliminated by shielding essentially all of the gastrointestinal tract during exposure to doses between 1,000 and 1,400 r, deaths attributable primarily to bone marrow damage occurred predominantly during the second postexposure week, with peak mortality falling on days 9 and 10. The LD/ sub 50/ is increased from about 650 r for whole-body exposure to approximately 900 r by this shielding procedure. The administration of bone marrow following exposure of animals shielded in this manner raised the LD/sub 50/ still higher to about 1,200 r; and 30% survival was obtained after 1,400 r. These data thus support the hypothesis that deaths associated with marrow damage can be prevented at x-ray doses considerably in excess of the whole-body LD/sub 50/ dose in the rat, and that an upper limit for protection against wholebody x-radiation by bone marrow injection in this species is that dose at which the early deaths associated with gut damage, which appears to be refractive to the treatment, becomes prominent. (auth)
- Research Organization:
- Naval Radiological Defense Lab., San Francisco
- NSA Number:
- NSA-12-010327
- OSTI ID:
- 4335850
- Report Number(s):
- USNRDL-TR-243
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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