HEMATOLOGIC EFFECTS OF RADIATION 



1037 



of cells to irradiation. Such observations should not be construed to 

 imply that sensitivity and rapidity of regeneration or functional reconsti- 

 tution are synonymous. Rates of regeneration from an atrophic hemato- 

 poietic tissue of various cell types differ markedly. 



The erythrocyte, hemoglobin, or hematocrit values of the peripheral 

 blood do not reflect this erythroblast sensitivity in animals such as 

 rabbits, rats, and mice unless the total-body exposure is above 300 r. On 

 the other hand, reticulocytes, which are the immediate precursors of the 

 erythrocytes, are significantly reduced in these species after total-body 

 irradiation at dosages of 100 r and above. The findings of Bloom on the 

 relative sensitivity of the erythroblast have been confirmed by Hennesey 

 and Huff (1950). These authors studied the depression of tracer iron 

 uptake (Fe 59 ) by rat erythrocytes following exposure to various dosages. 

 By this method they found that a significant inhibition of erythropoiesis 

 was apparent 24 hours after exposures as low as 5 and 25 r. On the basis 

 of available data from peripheral-blood studies, guinea pigs have the most 

 sensitive erythropoietic tissue of all the common laboratory animals. 

 Lorenz (1951) has shown that a severe anemia develops in guinea pigs 

 after exposure to 200 r, which is one-half the 30-day LD 50 for this species. 

 Dogs are more nearly comparable to the guinea pigs in this respect. 

 Rabbits, which are the most resistant of the common laboratory animals 

 to irradiation (LD 50 , 800 r), develop a less severe anemia after an LD 5 o 

 exposure than do dogs, cats, guinea pigs, or mice. This is apparent in 

 material presented by Valentine and Pearce (1952) (see Table 16-2). 



Table 16-2. Effect of Total-body X Irradiation on the Erythrocyte Values 



of the Peripheral Blood 



a References: (1) Lorenz, 1951; (2) Suter, 1947; (3) Lawrence, Dowdy, and Valen- 

 tine, 1948; (4) Bennett, Hanson, and Dowdy, 1951; (5) Jacobson et al., 1947; (6) 

 Prosser, Painter, and Swift, 1946; (7) Rekers, 1949. 



