Saturation and inversion transfer studies of creatine kinase kinetics in rabbit skeletal muscle in vivo

Abstract

The steady-state kinetics of the creatine kinase reaction in rabbit skeletal muscle in vivo was investigated using inversion and saturation magnetization transfer techniques. Both techniques determined the forward rate of this reaction (creatine phosphate ATP) as approximately 0.3 s-1. This corresponds to a flux of 10 mumol creatine phosphate/s/g muscle. The saturation transfer technique underestimated the reverse reaction by approximately 56%. This result is likely due to the participation of ATP in other interactions in skeletal muscle not involving creatine phosphate.

Magnetization‒transfer 31P NMR of biochemical exchange in vivo: Application to creatine kinase kinetics

“…Parameters describing flux through the forward CK reaction agree well with findings by other researchers, who did not assess the reverse reaction [17,18]. Consistent with animal studies, the ratio k −1 /k +1 is roughly three [14,15]. Underlining that the CK reaction is near equilibrium, approximately identical fluxes are observed for the forward and the reverse reactions, v for ≈ v rev .…”

“…Early examples include the adenylate kinase [10] and the ATPase reaction [11]. Flux through the CK reaction has been most extensively investigated by this approach including perfused organs [12,13], whole animals [14][15][16], and human subjects [7,[17][18][19][20][21][22]. The following discussion will focus on experiments designed to study the CK reaction in resting human skeletal muscle.…”

Interpretation of 31P NMR saturation transfer experiments: what you can't see might confuse you. Focus on “Standard magnetic resonance-based measurements of the Pi→ATP rate do not index the rate of oxidative phosphorylation in cardiac and skeletal muscles”

“…Steady-state saturation transfer experiments are sensitive to small pools of metabolites, while other magnetization transfer techniques relying on short pulsed magnetization transfer techniques such as inversion transfer (11,19,22) or two-dimensional (2D) NOESY NMR (3,25) experiments are not sensitive to small pools. This is due to the fact that the labeling of the pools only occurs over a very short period of time, making any transfer observed proportional to the size of the exchanging pools (19,25).…”

Inverse polarization transfer for detecting in vivo 13C magnetization transfer effect of specific enzyme reactions in 1H spectra

“…The difference spectrum showed significant intensity changes in Glu C2 at 55.7 ppm only. (a) The 1 H results obtained after infusion of [1,[6][7][8][9][10][11][12][13] C 2 ]glucose from the localized spectroscopy voxel (5 × 2.9 × 5 mm 3 ) in rat brain using the INEPT-based inverse 13 C-to-1 H heteronuclear polarization transfer technique. TR = 9.2 sec.…”

“…The LDH reaction and CA-catalyzed bicarbonate-carbon dioxide exchange have direct consequences to current 13 C metabolic imaging using infusion of hyperpolarized [1-13 C] pyruvate [5]. The fast exchange reactions Lac ↔ Pyr catalyzed by LDH and HCO 3 − ↔ CO 2 by CA can obviously be measured with high spatial resolution using hyperpolarized 13 C imaging combined with inversion transfer [6] or exchange spectroscopy (EXSY) methods [7]. 13 C MRS offers high spectral separation, thereby allowing clear discrimination of many metabolite resonances even at low magnetic field strength.…”