SUPPRESSION OF BETA-OXIDATION RESTORES PYRUVATE INHIBITION OF PYRUVATE-DEHYDROGENASE KINASE IN STARVED RAT-HEART

Kinetic behaviour of rat heart pyruvate dehydrogenase kinase (PDHK alp ha) was studied in the multi-enzyme complex (PDC) contained in two pre parations: mitochondria (mPDC) and a high speed pellet of Triton-extra cted tissue (hPDC). Two parameters were evaluated: V-av, related to V- max, and Fractional Pyruvate Inhibition (FPI). Starvation of rats for 48 h led to a rise in V-av and a fall in FPI. Injection into starved r ats of agents which reduce beta-oxidation of fatty acids restored, in succession, FPI and then V-av, of hPDC, to levels found in hPDC from f ed animals. In vitro incubation at 30 degrees C of hPDC from starved a nimals restored FPI, but not V-av, to 'fed' values; both were restored during in vitro incubation of mPDC from starved animals within the sa me time frame as in the in vivo experiments. A sharp increase of FPI, but not V-av, of hPDC from both fed and starved rats was observed in l ater experiments. This could have been due to differential selection o f the two genes for isoenzymes of PDHK alpha proposed by other workers .