Activation of pyruvate dehydrogenase by electrical stimulation, and low-Na+ perfusion of guinea-pig heart.
(1) Electrical stimulation (2 Hz) of guinea-pig hearts, perfused with medium containing 11 mM D-glucose plus 0.1 mM octanoate as substrate, resulted in an increase in the percentage of pyruvate dehydrogenase in the active form (PDHa) from 16 to 68%. (2) Rapid isolation of mitochondria by a technique designed to minimize net loss or gain of Ca2+ revealed an increase in mitochondrial Ca2+ content of the stimulated hearts, as measured with 45Ca (2.74 +/- 0.27 versus 1.37 +/- 0.11 nmol/mg protein; stimulated versus rested). (3) Perfusion of rested hearts with a medium containing a reduced Na+ concentration (20 mM, with the remainder replaced with Li+) also gave increased values of PDHa content (30.9% versus 16% for the normal, physiological medium). This procedure is known to raise cytosol Ca2+ concentrations and would be expected to give mitochondrial Ca2+ loading. (4) These results are consistent with a role of mitochondrial Ca2+ in activating pyruvate dehydrogenase in the intact heart.
Hansford
R G
RG
Laboratory of Cardiovascular Science, National Institute on Aging, Baltimore, MD.
Hogue
B
B
Prokopczuk
A
A
Wasilewska
E
E
Lewartowski
B
B
D000818:Animals; D002118:Calcium / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004558:Electric Stimulation; D004789:Enzyme Activation; D005260:Female; D006168:Guinea Pigs; D008094:Lithium / Q000378:metabolism; D008297:Male; D008929:Mitochondria, Heart / Q000378:metabolism*; D009243:NAD / Q000378:metabolism; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism*; D051381:Rats; D012964:Sodium / Q000378:metabolism*
D011768:Pyruvate Dehydrogenase Complex; D009243:NAD; D008094:Lithium; D012964:Sodium; D002118:Calcium