AMINO ACID INCORPORATION BY LIVER MICROSOMES 225 



TABLE I 



Effect of Phalloidin-Treatment in vivo on the Activity of Incorporation 

 Systems with Microsomes and RNP-Particles 



From livers of control and phalloidin-treated guinea-pigs microsomal fractions 

 [5] and RXP-particles [26] were isolated in parallel. The activities of these prepara- 

 tions were compared in the same way as in Fig. 2. 



* Macroscopic effects on liver. 



of mitochondrial functions, including P/0-ratio, respiratory control and 

 latent ATP-ase. 



It may be of some interest that the inhibitory effect of phalloidin on 

 the incorporation of labelled amino acids into protein was not confined 

 only to the cell-free systems. Similar effects were readily obtained with 

 liver slices under conditions when there is no histological evidence of any 

 appreciable intracellular disorganization (Table II). 



TABLE II 



Effect of Phalloidin on the Incorporation of [^^C]-dl-Valine into Protein 

 BY GuiNEA-PiG Liver Slices 



Incubation at 35° in Oo-CO., (95 : 5) gas phase. The tubes contained 80 mg. 

 of liver slices [12] in 2 ml. of a Krebs-Henseleit medium [18] including 0-025 ^^ 

 glucose. Addition of 1-34 fimoles of [^*C]-DL-valine (0-14 mC/mmole) at the 

 beginning of incubation or after 60 min. of preincubation. 



Incubation after the addition of [^*C]-DL-valine 45 min. 



It is not known yet by which modification of the membrane functions 

 phalloidin exerts its inhibitory effects on the incorporation activity of the 

 microsomes. The effect seems not to be due to an induction of ATP-ase 

 in the membranes. As is shown by Table III about 25% of the ATP and 

 PEP added to the incorporation system was broken down to orthophosphate 

 in the course of the incubation, but no increased phosphate formation was 



Q 



