ENDOTOXIN-PROTECTION OF MICE. THE RELATIONSHIP TO COLONY-FORMING UNITS
NAVAL RADIOLOGICAL DEFENSE LAB SAN FRANCISCO CA
Pagination or Media Count:
Earlier studies have shown that bacterial endotoxins increase survival of irradiated animals. Although these substances do not confer as much protection as do the classical chemical protectants, endotoxins do significantly increase survival when given either before or for a short time following irradiation. The mechanisms of endotoxin protection have not been clearly established, but earlier studies have shown that hematopoietic stimulation is involved. The present studies were designed to evaluate the effects of endotoxin on proliferative cells in the hematopoietic system. Methods have recently been devised to measure the numbers of certain proliferative cells within the bone marrow, spleen, and other hematopoietic sites. These proliferative cells are called colony-forming units CFUs, and their numbers are estimated by counting the colonies or nodules in the spleens of irradiated mice which arise either spontaneously or after injection of hematopoietic cells. The present data indicate that endotoxin does not alter the radiosensitivity of endogenous splenic CFUs the D37 for CFUs is approx. 90 R in both endotoxin-treated and control mice. When endotoxin is injected at the time which produces optimal survival, the femur content of CFUs increases approx. 2 fold whereas, the spleen content of CFUs is increased approx. 20 fold. The increased rate of CFUs migration from the femur to the spleen in endotoxin-treated animals may contribute to the relatively greater increase in splenic CFUs.