| Summary: | Glycolysis, measured by ³H₂0 production from [5-³H]-glucose, is accelerated in
isolated working hypertrophied rat hearts. However, non-glycolytic detritiation of [5- ³H]-
glucose by transaldolase in the non-oxidative pentose phosphate pathway (PPP) could
lead to an overestimation of true glycolytic rates. Since the PPP may be upregulated in
cardiac hypertrophy, I tested the hypothesis that detritiation of [5-³H]-glucose does not
overestimate glycolysis in hypertrophied hearts and that accelerated rates of glycolysis
reported in hypertrophied hearts are real and not artifactual. Glycolysis was measured by
three independent methods in isolated working hearts from halothane-anesthetized shamoperated
(Control) and aortic-constricted (Hypertrophy) rats. Two of the three methods
determined glycolytic rates by quantifying the accumulation of glycolytic end products in
timed collections of perfusate while the last method determined glycolytic rates by
detritiation of [5-³H]]-glucose in the glycolytic pathway by production of 3H₂0. The first
method involved enzymatic determination of lactate and pyruvate combined with rates of
glucose oxidation. The second method involved determination of radiolabeled [¹⁴C]-
lactate and [¹⁴C]-pyruvate accumulation combined with rates of glucose oxidation. The
third method, which measures glycolytic flux by metabolism of [5-³H]-glucose, was in
question and thus was used for comparison with the aforementioned alternative methods
of determining glycolytic flux. Glycolysis was accelerated in hypertrophied hearts,
regardless of the method used. There was also excellent concordance between the three
methods with no significant differences in glycolysis detected between corresponding
groups. Moreover, glucose-6-phosphate dehydrogenase activity and transaldolase
expression, enzymes controlling key steps in the oxidative and non-oxidative PPP,
respectively, were not different between control and hypertrophied hearts. Thus, nonglycotytic
loss of 3H₂0 from [5-³H]-glucose is insignificant and 3H₂0 production from [5-³H]-
glucose is an accurate means to measure glycolysis in isolated working normal and
hypertrophied rat hearts. Furthermore, the PPP does not appear to be increased in this model of
cardiac hypertrophy. === Medicine, Faculty of === Pathology and Laboratory Medicine, Department of === Graduate
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