³¹P magnetization transfer studies in the monkey brain

Abstract

The forward and reverse rates through the creatine-kinase (CK) catalyzed reaction, phosphocreatine + ADP + H⁺ creatine + ATP in the in vivo monkey brain were measured using the techniques of saturation transfer (ST) and inversion transfer (IT) ³¹P nuclear magnetic resonance (NMR) spectroscopy. Independent checks on the ST apparent longitudinal relaxation (τ) data could be obtained from the parameters determined from the IT analyses. At near-equilibrium it is assumed that the forward-to-reverse flux ratio lies close to 1.0. In the monkey brain the value for the forward-to-reverse flux ratio obtained is 1.37 ± 0.26 calculated from ST with average τ values from IT initial slopes, a value which is not significantly different from unity. The present NMR data point to the CK reaction in the living monkey brain being maintained at or near equilibrium.