EFFECTS OF IN VIVO AND IN VITRO IRRADIATED BONE MARROW ON THE LIVER REGENERATION OF RATS

Experiments were conducted to determine: whether irradiated bone marrow can cause the appearance of general irradiation symptoms in recipient rats; what differences can be observed in liver regeneration of rats when normal or 500-r irradiated bone marrow suspension is introduced; and whether there is any difference in the effects caused by direct irradiation of bone marrow, by in vivo irradiated bone marrow suspension obtained from irradiated animals, or by in vitro irradiated bone marrow suspension. Partial removal of the liver of 222 rats was performed, and they were x irradiated 24 hr after hepatectomy with 100, 200, irradiated rats, the iliac crest was shielded with Pb during the irradiation period. The in vivo irradiated bone marrow was removed from the rats 1 to 2 hr postirradiation, suspended in saline, and injected into the test animals. The in vitro irradiated bone marrow suspension was obtained from normal rats, irradiated in a test tube, and injected into test animals. The bone marrow injections were made the day after partial hepatectomy. After 100 r the mortality of rats not receiving marrow injections was 0%, regeneration of liver 2.00 g/100 g body wt, and percentage of liver regenerating 70.7%; the corresponding values at 200more » r were 16.6%, 1.90 g, 65.2%; at 300 r 20%, 1.86 g, 64.3%; at 400 r 16.6%, 1.77 g, 60.5%; at 500 r 25%, 1.61 g, 62.5%; at 700 r 37.5%, 1.58 g, 61.3%; at 1000 r 50%, 1.38 g, 50.1%. The in vitro irradiated bone marrow produced a similar effect but was somewhat less effective in the percentage of regeneration. The suspension irradiated at 100, 200, and 300 r increased the regeneration process, at 400 r no effect was noted, and at greater doses regeneration was hindered. The in vivo and in vitro irradiated bone marrow suspension did not increase the mortality rate significantly. It was concluded that irradiation of bone marrow impedes the regeneration of liver in rats significantly. The beneficial effects of normal bone marrow suspension on liver regeneration are abolished when it is irradiated in vitro, except at the lower doses (100, 200, and 300 r) of radiation. (BBB)« less