Functional compartmentation of glycolytic versus oxidative metabolism in isolated rabbit heart.

Abstract

To investigate whether energy derived from glycolytic and oxidative metabolism are preferentially used for different functions in heart, tension, intracellular potential, and extracellular [K+] and pH (using triple barrel K/pH electrodes, tip diameter 0.5 mm) were monitored in isolated arterially perfused rabbit interventricular septa during exposure to hypoxia and metabolic inhibitors. Myocardial content of high energy phosphates, lactate, and glycogen were determined under the same conditions. Inhibiting oxidative metabolism with hypoxia, dinitrophenol (10-s M), or Na-azide (10-3 M) caused marked suppression of tension (by 73±5, 65±8, and 50±14%, respectively) and a small increase in [K+]> (0.8±0.4, 0.5±0.25, and 0.4±0.2 mM, respectively) after 10 min. Inhibiting glycolysis with iodoacetate (IAA) (10-3 M) had a much smaller suppressant effect on tension (28±24%) but markedly increased IK'io accumulation (by 1.8±1.1 mM) at 10 min. These differences, when IAA was compared individually to the other interventions, were highly significant. The shortening of action potential duration was not significantly different for the four interventions. pHO increased slightly during IAA (+0.04-+0.06 U) and fell during the other interventions (-0.10--0.16 U), but this did not account for the differences in [K+]J accumulation and tension between inhibition of glycolytic vs. oxidative metabolism. Except for hypoxia, total cellular content of high energy phosphates was not significantly depressed under the various conditions. This data suggests that energy from glycolysis is preferentially used to support sarcolemmal function (as manifested by K+ loss), whereas oxidatively derived energy preferentially supports contractile function.

Interaction of Cofilin with Triose-phosphate Isomerase Contributes Glycolytic Fuel for Na,K-ATPase via Rho-mediated Signaling Pathway

“…It is believed that oxidative ATP supports the mechanical activity of the cell, whereas glycolytic ATP fuels energy for membrane functions (38). Indeed, many membrane proteins such as the ATP-sensitive K ϩ channel, Ca 2ϩ pump, Na,K-ATPase, and L-type Ca 2ϩ channel, are known to use glycolytic ATP preferentially rather than oxidative ATP (39).…”

Maturation of Cerebral Oxidative Metabolism in the Cat: A Cytochrome Oxidase Histochemistry Study

“…In the case of 2DG, rates of metab olism are calculated in terms of f.Lmol glucose min -I g-l of tissue, However, with currently available techniques CO can only be measured in terms of density of stain, thereby being only a reflection of, as opposed to directly measuring, oxidative rate. Finally, recent studies on both the heart (Weiss and Hiltbrand, 1985;Higgins and Bailey, 1983;Brick nell and Opie, 1978) and brain (Andersen and Mar marou, 1989b;Andersen and Marmarou, 1989a;Braun et aI., 1985) indicate that glucose is used pri marily for maintaining the membrane ionic gradient, whereas oxidative metabolism is broader and in cludes other energy demands of the cells. Conse quently, the difference during development of these two metabolic processes may reflect the cell's pref erence early in life for morphological growth and the installment of machinery for biochemical pro cesses while the processes required for intercellular communication are deferred until later in develop ment.…”

Persistent Changes in Myocardial Glucose Metabolism In Vivo During Reperfusion of a Limited-Duration Coronary Occlusion

“…Evidence suggests myocardial energy metabolism is compartmentalized such that ATP formed in the cytosol by glycolysis is used preferentially to support homeostatic processes (eg, ion transport), whereas ATP formed oxidatively in mitochondria supports mechanical work. 22 Glycolysis may in fact be functionally coupled to sarcoplasmic reticulum calcium transport, 23 a process whose impairment may contribute to postischemic stunning. 24 Thus, increased glycolytic flux during reperfusion, even if not a large fraction of total ATP production, may contribute to maintaining cellular viability.…”