Transmural gradients of glycolytic enzyme activities in life ventricular myocardium

Transmural high energy phosphate distribution and response to alterations in workload in the normal canine myocardium as studied with spatially localized 31P NMR spectroscopy

“…DISCUSSION Spectroscopic spatial localization. Previous studies of 0 2 consumption rate ( 5 , 6 ) , p 0~ ( 7, 8), mechanical work ( 1-4), and distribution of enzymes involved in cellular bioenergetics (8,(13)(14)(15) have demonstrated that the LV wall is not biochemically homogeneous even under normal physiological conditions. Recently developed approaches based on spatially localized NMR spectroscopy provide the ability to examine the consequences of this heterogeneity on the transmural HEP content and the regulation of oxidative phosphorylation.…”

“…In consequence, oxygen tension within the LV wall decreases progressively toward the LV chamber ( 7 , 8) and the subendocardial region becomes most susceptible to insufficiencies of O2 supply that may occur even in the normal heart at elevated heart rates and workloads. This transmural heterogeneity in O2 supply and demand, coupled with the previously documented transmural diversity in the levels of enzymes involved in ATP synthesis (8,(13)(14)(15) raise the possibility that the concentrations of substrates for the oxidative phosphosphorylation process and high energy phosphates (HEP) may also be nonuniform across the LV wall and may show transmural variation in their response to alterations in heart rate and workload. We have examined this question by measuring the myocardial HEP and "free" ADP content with transmural differentiation at different workloads and phases of the cardiac cycle using a recently developed spatially localized NMR spectroscopy technique ( 1 6 ) .…”

Epicardial and endocardia1 localized 31p magnetic resonance spectroscopy: evidence for metabolic heterogeneity during regional ischemia

“…Heterogeneity of high energy phosphates and other compounds across normal myocardium has been suggested by previous studies using direct biochemical measurements ( 24,25). Most measurements of blood flow under normal conditions have demonstrated uniform transmural flow (24, 25) with differences in metabolites attributed to transmural differences in myocardial wall stress or energy expenditure (26).…”

Metabolism of [3-13C]pyruvate and [3-13C]propionate in normal and ischaemic rat heart in vivo: 1H- and 13C-NMR studies

“…That is, there are cells which gain energy mainly from glycolysis and produce lactate, while other cells obtain energy from the oxidation of substrates (such as lactate) and produce alanine. Although there is no direct morphological evidence for such heterogeneity of the cell population, there are data suggesting heterogeneity of heart contractile function [21,22], oxygen consumption [23,24] and in the distribution of glycolytic enzymes [25]. These data may support the idea that different regions in the heart perform preferential oxidative metabolism or preferentially use glycolysis as energy source, and these heterogeneities can cause different labelling patterns in lactate and alanine.…”