AMINO ACID INCORPORATION BY LIVER MICROSOMES 



TABLE VII 



231 



Effect of X-Irradiation or Prednisolone Treatment in vivo on RNA-Content 

 AND [i^C]-l-Leucine Incorporation Activity of Mitochondria-Free Rat 



Liver Homogenates 



X-rays (all body irradiation, 45 min. 2500 r) and prednisolone (50 mg/kg. body 

 weight, intraperitoneal injection) 21 hr. prior to decapitation. Incubation as in 

 Table V. 



Incorporation and RNA content in 

 per cent of controls 



X-irradiation 



prednisolone 



[^*C]-L-leucine incorporation 

 RNA content 



282 

 no 



455 

 120" 



* Cf. [20]. 



Experimental evidence has been advanced by Mole [21] that the effect 

 of irradiation on the content of liver glycogen depends on an increased 

 susceptibility of the liver cells to corticoids. The following facts indicate 

 that the increased incorporation activity described in this section has a 

 similar relationship to corticoid functions: {a) The activation normally 

 observed 20 hr. after aminofluorene treatment was absent in adrenalec- 

 tomized animals (Table VIII). As a matter of fact, an inhibition was 



TABLE VIII 



Effect of 2-Aminofluorene-Treatment in vivo on the Incorporation of 

 ["C]-l-Leucine into Protein by Mitochondria-Free Homogenates from 

 Adrenalectomized Rats 



The rats were adrenalectomized 48 hr. before the incorporation experiment. 

 Experimental conditions as in Table V, 2-aminofluorene (AF) being administered 

 21 hr. prior to decapitation. 



Pre-treatment in vivo 



c.p.m./cm'^ 



Adrenalectomized controls 

 Adrenalectomized, AF (o'5 mmole/kg.) 

 Adrenalectomized, AF (10 mmole/kg.) 



441 



389 

 308 



usually observed ; {b) Activation effects similar to those obtained in the rat 

 with 2-aminofluorene, 2-aminonaphthalene or X-irradiation were obtained 

 after the intraperitoneal administration of prednisolone (Table VII). 

 These experiments are consistent with the recent observations by Feigelson 

 et al. [9] that cortisone enhances the amino acid incorporation by rat liver 

 in vivo. 



Not very much can be said at present about the working mechanisms 



