EFFECTS ON VARIOUS METABOLIC PATHWAYS 



307 



correlated and a general picture of maleate action emerge, so that one can 

 better understand the effects of maleate on growth and certain tissue func- 

 tions in the whole animal. 



Amino Acid Synthesis in Liver and Kidney 



The synthesis of amino acids by transamination can under certain cir- 

 cumstances deplete the cycle, and this is probably one of the important 

 regulatory mechanisms involved in the over-all response to maleate. If 

 a-ketoglutarate is incubated with rat liver mitochondria under the condi- 

 tions used by Rogulski et al. (1962), 40% is oxidatively decarboxylated. 

 When NH4+ is added, 90% of the «-ketoglutarate is utilized and amino 

 acids are formed; NH4+ in liver shifts the metabolism of a-ketoglutarate 

 toward amino acid synthesis. Addition of NH4+ to kidney mitochondria 

 in the presence of a-ketoglutarate, on the other hand, has much less effect 

 and relatively little amino acid is formed. This system is more sensitive 

 to maleate in the kidney than in the liver (Table 2-4) and similar results 



Effect of Maleate on 



Table 2-4 



-Ketoglutarate Metabolism in Liver and Kidney 

 Mitochondria " 



" Incubation at pH 7.2 and 38" for 1 hr, the initial concentration of a-ketogultarate 

 being 20 mM and NH4+ 20 mM. (From Rogulski et al., 1962.) 

 * Value is approximate because so little amino acid formed. 



