THE HAEMATOPOIETIC REGENERATION IN WHOLE BODY IRRADIATED RATS 



tissues of these rats is quite similar to that observed in rats receiving a lethal 

 irradiation of 800 r. The daily injection of 3 or 5mg of D.C.A. does not 

 modify the regeneration of haematopoietic tissues. 



{2) Influence of adrenalectomy on the haematopoietic regeneration 



Methods : four groups of rats were used. The animals of the first group are irradiated 

 with a lethal dose of X-rays (800 r) . The rats of the second group are adrenalectomized 

 and 4 days later submitted to 800 r. The animals of the third group and the fourth 

 group are adrenalectomized and irradiated. In addition, they were supplemented 

 with a dose of D.C.A. (3 mg daily) or cortisone (2-5mg daily) too small to influence 

 the haematopoietic activity. The haematopoietic tissues are taken and studied 

 histologically between the fourth day and the moment of death. 







4^1^%... 



Figure 2. Femoral bone marrow of the rat, 15 days after 500 r and injection of 

 cortisone acetate ( 1 mg daily) : inhibition of the myelopoiesis {200 X ) 



The control rats receiving 800 r died between the sixth and the tenth 

 day. They never showed any repair of the haematopoietic tissues destroyed 

 by the irradiation. The adrenalectomized rats were very sensitive to a 

 lethal dose of X-rays (800 r) and died before any regeneration could possibly 

 take place (fourth day). In the adrenalectomized group of rats supple- 

 mented with a dose of D.C.A. (3 mg daily) or cortisone (2 • 5 mg) the resistance 

 appeared to be normal. Some of them survived for 10 days. Although any 

 possibility of hypercorticism was excluded, no haematopoietic regeneration 

 has been observed in these rats. 



The results of these experiments are not conclusive. Should an increased 

 adrenocortical secretion be able to inhibit the haematopoietic regeneration, 

 there is no doubt that the hypercorticism following a lethal whole body 

 irradiation is not the only factor involved in the inhibition of haematopoiesis. 

 The adrenalectomy does not succeed, indeed, in stimulating the haemato- 

 poietic regeneration of irradiated rats. Some other factors must be involved 

 in the regulation of this phenomenon. 



294 



