Control of pyruvate dehydrogenase activity in intact cardiac mitochondria. Regulation of the inactivation and activation of the dehydrogenase.

Phenylephrine, vasopressin and glucagon each increased the amount of active (dephospho) pyruvate dehydrogenase (PDHa) in isolated rat hepatocytes. Treatment with 4 beta-phorbol 12-myristate 13-acetate (PMA) opposed the increase in PDHa caused by both phenylephrine and glucagon, but had no effect on the response to vasopressin: PMA alone had no effect on PDHa. As PMA is known to prevent the phenylephrine-induced increase in cytoplasmic free Ca2+ concentration ([Ca2+]c) and to diminish the increase [Ca2+]c caused by glucagon, while having no effect on the ability of vasopressin to increase [Ca2+]c, these data are consistent with the notion that in intact cells an increase in [Ca2+]c results in an increase in the mitochondrial free Ca2+ concentration, which in turn leads to the activation of PDH. In the presence of 2.5 mM-Ca2+, glucagon caused an increase in NAD(P)H fluorescence in hepatocytes. This increase is taken to reflect an enhanced activity of mitochondrial dehydrogenases. PMA alone had no effect on NAD(P)H fluorescence; it did, however, compromise the increase produced by glucagon. When the extracellular free [Ca2+] was decreased to 0.2 microM, glucagon could still increase NAD(P)H fluorescence. Vasopressin also increased fluorescence under these conditions; however, if vasopressin was added after glucagon, no further increase in fluorescence was observed. Treatment of the cells with PMA resulted in a smaller increase in NAD(P)H fluorescence on addition of glucagon: the subsequent addition of vasopressin now caused a further increase in fluorescence. Changes in [Ca2+]c corresponding to the changes in NAD(P)H fluorescence were observed, again supporting the idea that [Ca2+]c indirectly regulates intramitochondrial dehydrogenase activity in intact cells. PMA alone had no effect on pyruvate kinase activity, and the phorbol ester did not prevent the inactivation caused by glucagon. The latter emphasizes the different mechanisms by which the hormone influences mitochondrial and cytoplasmic metabolism.

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Effects of glycogen stores and non-esterified fatty acid availability on insulin-stimulated glucose metabolism and tissue pyruvate dehydrogenase activity in the rat

Diabetologia ◽

10.1007/bf00405077 ◽

1991 ◽

Vol 34 (4) ◽

pp. 205-211 ◽

Cited By ~ 22

Author(s):

Y. T. Kruszynska ◽

J. G. McCormack ◽

N. McIntyre

Keyword(s):

Fatty Acid ◽

Glucose Metabolism ◽

Dehydrogenase Activity ◽

Pyruvate Dehydrogenase ◽

Glycogen Stores

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Regulation of Glucose Metabolism by Altered Pyruvate Dehydrogenase Activity. I. Potential Site of Insulin Resistance in Sepsis

Journal of Parenteral and Enteral Nutrition ◽

10.1177/0148607186010004351 ◽

1986 ◽

Vol 10 (4) ◽

pp. 351-355 ◽

Cited By ~ 20

Author(s):

Thomas C. Vary ◽

John H. Siegel ◽

Toshio Nakatani ◽

Toshihide Sato ◽

Hidehisa Aoyama

Keyword(s):

Insulin Resistance ◽

Glucose Metabolism ◽

Dehydrogenase Activity ◽

Pyruvate Dehydrogenase ◽

Potential Site

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Glucose metabolism in perfused skeletal muscle. Pyruvate dehydrogenase activity in starvation, diabetes and exercise

Biochemical Journal ◽

10.1042/bj1580203 ◽

1976 ◽

Vol 158 (2) ◽

pp. 203-210 ◽

Cited By ~ 65

Author(s):

S A Hagg ◽

S I Taylor ◽

N B Ruberman

Keyword(s):

Skeletal Muscle ◽

Dehydrogenase Activity ◽

Pyruvate Dehydrogenase ◽

Preceding Paper ◽

Diabetic Rats ◽

Pyruvate Dehydrogenase Kinase ◽

Lactate Oxidation ◽

Pyruvate Oxidation ◽

Measured Activity ◽

Exercise Induced

1. The interconversion of pyruvate dehydrogenase between its inactive phosphorylated and active dephosphorylated forms was studied in skeletal muscle. 2. Exercise, induced by electrical stimulation of the sciatic nerve (5/s), increased the measured activity of (active) pyruvate dehydrogenase threefold in intact anaesthetized rated within 2 min. No further increase was seen after 15 min of stimulation. 3. In the perfused rat hindquarter, (active) pyruvate dehydrogenase activity was decreased by 50% in muscle of starved and diabetic rats. Exercise produced a twofold increase in its activity in all groups; however, the relative differences between fed, starved and diabetic groups persisted. 4. Perfusion of muslce with acetoacetate (2 mM) decreased (active) pyruvate dehydrogenase activity by 50% at rest but not during exercise. 5. Whole-tissue concentrations of pyruvate and citrate, inhibitors of (active) pyruvate dehydrogenase kinase and (inactive) pyruvate dehydrogenase phosphate phosphatase respectively, were not altered by excerise. A decrease in the ATP/ADP ratio was observed, but did not appear to be sufficient to account for the increase in (active) pyruvate dehydrogenase activity. 6. The results suggest that interconversion of the phosphorylated and dephosphorylated forms of pyruvate dehydrogenase plays a major role in the regulation of pyruvate oxidation by eomparison of enzyme activity with measurements of lactate oxidation in the perfused hindquarter [see the preceding paper, Berger et al. (1976)] suggest that pyruvate oxidation is also modulated by the concentrations of substrates, cofactors and inhibitors of (active) pyruvate dehydrogenase activity.

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