Selectively Eliminated Blood Monocytes and Splenic Suppressor Macrophages in Mice Depleted of Bone Marrow by Strontium 89

摘要

The contribution of specific activity to the effects of the bone-seeking isotope, strontium 89 on radiosensitive components of mononuclear phagocyte populations was investigated in mice. CBA/J mice received a fixed dose of 2 microcuries/g body weight of SR89 with three different specific activities, 6 Ci, 100 microcuries and 20 Sr89 microcuries per mg Sr. The estimated radioactivity located in the bone surface was 4,200, 3,000 and 2,400 cpm/mg bone when measured 2 days after the administration of SR89, and was lost with an estimated biological half-life of 27, 25, and 23 days, respectively. Bone marrow suppression was assessed by quantitation of the depletion of macrophage-colony forming cells (M-CFC) grown in vitro. The decline in M-CFC closely paralleled the level of radioactivity in the bone. These effects were clearly reflected by the depletion of monocytes in the blood, which were reduced to 14%, 14%, and 21% of control levels corresponding to SA's of 6 Curies/mg, 100 microcuries/mg and 20 microcuries/mg when counted on day 10. By day 30 the respective monocyte levels were 15%, 31%, and 77%. Furthermore, the induction of prostaglandin E producing suppressor macrophages (marophages) by Corynebacterium parvum administration was found to vary inversely with the effects of radioactivity in the bone, with initial impairment followed by quantitative recorvery. Resident-type Macrophages in impairment cavity appear to be unaffected by Sr 89-treament. These data suggest that the monocytes and suppressor Macrophages are dependent on radiosensitive marrow cells.