EFFECTS OF PYRUVATE ON PYRUVATE-DEHYDROGENASE KINASE OF RAT-HEART

Sensitivity of rat heart pyruvate dehydrogenase kinase (PDHK) to pyruv ate inhibition was tested under various conditions using pyruvate dehy drogenase complex (PDC) in mitochondria (mPDC) and in a high speed pre cipitate of whole tissue homogenates (hPDC). In the latter preparation pyruvate in the range of concentration 1-10 mM caused increasing inhi bition of PDHK when the enzyme was prepared from animals fed ad libitu m but had no effect when the enzyme was prepared from 48 h starved ani mals. Similar behaviour was observed in mPDC from fed and starved anim als when rotenone was present in the incubation medium. When carbonyl cyanide m-chlorophenylhydrazone (CCCP) instead of rotenone was present , pyruvate at 1 mM concentration stimulated PDHK from hearts of fed an imals but was without effect at 10 mM. When mPDC or hPDC from hearts o f starved animals was incubated at 30 degrees C for 30 min, inhibition of PDHK by pyruvate was restored.