Analysis of compartmentation of ATP in skeletal and cardiac muscle using 31P nuclear magnetic resonance saturation transfer

Abstract

We have developed a model for the analysis of the forward creatine kinase reaction in muscle as measured by the nuclear magnetic resonance (NMR) technique of magnetization transfer. The model, accounting for the double-exponential behavior observed in some NMR magnetization transfer data, allows for the existence of two ATP pools, one that is NMR-visible (NMR-VIS) and another that is NMR-invisible (NMR-INVIS). We have applied the model to experimental data for the forward creatine kinase reaction in skeletal and cardiac muscles to study the dependence of the creatine kinase rate constants and fluxes on workload and to account for the differences between heart and skeletal muscle. The results suggest that an NMR-distinct ATP pool exists in both heart and skeletal muscles, and that phosphate exchange with this pool catalyzed by creatine kinase increases with increased workload. The results also agree with previously published estimates of the rates of mitochondrial translocase and net ATP synthesis obtained by traditional biochemical methods.

Dipolar coupling and ordering effects observed in magnetic resonance spectra of skeletal muscle

“…[64][65][66] Compartmentation and subsequent transport of water across the sarcolemma, i.e. the membrane around the multinuclear muscle cell, has been observed in a 1 H-MRS study by contrast-agents applied to the extracellular space.…”

“…This measurement alone does not necessarily contain information on biological order, however, some findings can be explained by different compartments. [64][65][66] Magnetization transfer indicates that there is a motionally restricted proton pool in spin-exchange with free Cr/PCr. [42][43][44] Since MT effects on the Cr/PCr methyl groups do not change after death in an animal study, 42 it is concluded that both creatine and phosphocreatine contribute to the MT effect.…”

Use of gene targeting for compromising energy homeostasis in neuro-muscular tissues: The role of sarcomeric mitochondrial creatine kinase

“…Fig. 2F,G), or point to the existence of a pool of ATP at the mitochon drial compartment with properties requiring a different NMR magnetization transfer technique for their detection in these tissues (Zahler et al, 1987). Likewise, in our studies of twitch force, tetanic force, force during repeated isometric contractions, or half relax ation times we may have missed specific physiological manifestations because more adequate protocols must be designed to challenge the enzymatic network involved in aerobic long-term muscle performance sufficiently.…”

Phosphorylation of chicken brain‐type creatine kinase affects a physiologically important kinetic parameter and gives rise to protein microheterogeneity in vivo

“…Recently, it has been demonstrated that enolase, an enzyme catalyzing a reversible step in the glycolytic pathway, is phosphorylated by protein kinase C (PKC) and that this posttranslational modification has inverse effects on both reaction directions [7]. Potentially, mechanisms controlling the performance of cytosolic CK isoenzymes together with mechanisms specifying their subcellular distribution could determine local intracellular ATP levels, for the latter nucleotide is not homogeneously distributed within cells, but rather exists in compartmentalized pools [8,9]. Microheterogeneity of ATP distribution throughout the cytosol, however, also can occur independent of compartmentation by membranes [lo], possibly due to the In this context B-CK, which has been found associated with synaptic vesicles [16,17] seemed of particular interest.…”