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

Abstract

The wide chemical shift dispersion and long T 1 of 13 C have allowed determination of in vivo magnetization transfer effects caused by aspartate aminotransferase and lactate dehydrogenase reactions using 13 C MRS. In this report, we demonstrate that these effects can be observed in the proton spectra by transferring the equilibrium magnetization of 13 C via the one-bond scalar coupling between 13 C and 1 H using an inverse INEPT-based heteronuclear polarization transfer method. This inverse method allows a combination of the advantages of the long 13 C T 1 for maximum magnetization transfer and the high sensitivity of proton detection. The feasibility of this in vivo inverse polarization transfer approach was evaluated for detecting the 13 C magnetization transfer effect of aspartate aminotransferase and lactate dehydrogenase reactions from a 72.5 μL voxel in the rat brain at 11.7 Tesla.

Glutamate and glutamine: a review of in vivo MRS in the human brain

“…Given the large gyromagnetic ratio and natural abundance of proton signal, these methods provide much greater SNR and ease of localization. Methods such as single‐shot multiple‐quantum coherence spectroscopy and J ‐difference editing can be used for the indirect detection of 13 C signal in Glu as well as polarization transfer . Methods such as single‐shot inversion recovery based non‐echo (SIRENE) 2D localization methods can be used to detect Glu as well as metabolites with very short T 1 and T 2 such as glycogen .…”

Characterization of Carbonic Anhydrase In Vivo Using Magnetic Resonance Spectroscopy

“…By introducing exogenous 13 C-labeled substrates, certain metabolic pathways can be studied using 3 of 16 in vivo 13 C MRS [36,37]. In our laboratory, several methods including an inverse detection method have been developed to measure different enzymatic reactions and their rate constants in vivo using 13 C MRS [38][39][40][41][42][43].…”

“…It has become a very useful and versatile tool for both clinical and basic science studies because it can measure concentrations of many important endogenous and exogenous molecules [37]. Our laboratory discovered the phenomenon of in vivo enzyme-specific 13 C magnetization transfer [38][39][40][41][42][43] and developed in vivo 13 C magnetization transfer MRS techniques for measuring carbonic anhydrase-catalyzed interconversion between carbon dioxide and bicarbonate [40]. We first quantified the in vivo rate of bicarbonate dehydration in the rodent brain and the effect of acetazolamide administration on the catalytic action of CA [40].…”