Influence of Bradykinin on Glucose Uptake and Metabolism Studied in Isolated Cardiac Myocytes and Isolated Perfused Rat Hearts

Quantification of myocardial glucose uptake by positron emission tomography with [18F]fluorodeoxyglucose (FDG) requires the “lumped constant” (LC), which corrects the difference of affinity between glucose and FDG to glucose transporters and phosphorylating system. Since LC was introduced, it has been considered to be constant. However, this has recently been questioned. To elucidate the constancy of LC by other than radioisotope techniques, the accumulation rate of sugar phosphates (d[SP]/d t) was measured in isolated, perfused rat hearts by31P NMR spectroscopy with 2-deoxyglucose (DG). We postulate α as the affinity of DG to transporters and the phosphorylating system relative to that of glucose. Theoretically, α is equivalent to LC. We determined α by measuring d[SP]/d t at DG concentration ([DG]) = 10, 7, 5, and 3 mmol/l, keeping the total of glucose concentration ([glucose]) and [DG] to 10 mmol/l. When the glucose uptake was enhanced by insulin (10 mU/ml) or stunning, calculated α was reduced (insulin stimulated, 0.15; stunning, 0.19) compared with the control (0.59). These results indicate that LC can be evaluated by methods without radiolabeled tracers and is smaller when glucose uptake is augmented.

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Lactate transport by cardiac sarcolemmal vesicles

AJP Cell Physiology ◽

10.1152/ajpcell.1987.253.1.1 ◽

1987 ◽

Vol 253 (1) ◽

pp. 1-1 ◽

Cited By ~ 21

Author(s):

T. L. Trosper ◽

K. D. Philipson

Keyword(s):

Cardiac Myocytes ◽

Rabbit Heart ◽

Lactate Transport ◽

Cardiac Sarcolemma ◽

Rat Hearts ◽

Least Squares Fit ◽

Perfused Rat Hearts ◽

Isolated Cardiac Myocytes ◽

Lactate Uptake ◽

Sarcolemmal Vesicles

Page C483: T. L. Trosper and K. D. Philipson. “Lactate transport by cardiac sarcolemmal vesicles.” Page C483: the first sentence of paragraph 2 should read: Recent reports of lactate uptake by isolated cardiac myocytes (14) and perfused hearts (2, 16) presented evidence suggesting that lactate traversal of the cardiac sarcolemma is mediated by a carrier specific for monocarboxylic acids. Page C485: Fig. 1 legend should read: l-Lactate uptake into sarcolemmal vesicles as a function of time at room temperature. 1 mM l-lactate in external medium; vesicles loaded with 280 mM sucrose, pH 7.4. External media: 112 mM NaCl, 56 mM sucrose, pH 7.4, with ( closed circles) or without ( open circles) 5 μM monensin; or 280 mM sucrose, pH 7.4 (X) or 5.9 ( open squares). Data points on upper curves are means ± SD of 3 or more experiments. Lower curves are averages of 2 experiments. Inset: l-lactate uptake at short times from NaCl plus monensin, pH 7.4. Page C485: last line of Fig. 3 legend should read: Slope, which is least-squares fit of the data, gives apparent Km, for l-laxtate of 27 mM. Page C489: References 2, 14, and 16 should read: 2. Dennis, S. C., M. C. Cohn, G. J. Anderson, and D. Garfinkel. Kinetic analysis of monocarboxylate uptake into perfused rat hearts. J. Mol. Cell. Cardiol. 17: 987–995, 1985. 14. Kammermeier, H., B. Wein, and W. Graf. Characteristics of lactate transport in isolated cardiac myocytes. Basic Res. Cardiol. 80,Suppl. 1:57–60, 1985. 16. Mann, G. E., B. V. Zlokovic, AND D. L. Yudilevich. Evidence for a lactate transport system in the sarcolemmal membrane of the perfused rabbit heart. Biochim. Biophys. Acta 819: 241–246, 1985.

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