PHOSPHORUS J-COUPLING-CONSTANTS OF ATP IN HUMAN MYOCARDIUM AND CALF MUSCLE

Proton-decoupled P-31 NMR spectroscopy of the heart and calf muscle of healthy volunteers was performed with a 1.5 T whole-body imager. By u se of two-dimensional chemical-shift imaging in combination with slice -selective excitation, well-resolved localized spectra (elements of 38 mi) were obtained within 20 to 35 min from which the homonuclear J co upling constants of ATP could be determined. In myocardium, J(gamma be ta) = 16.03 +/- 0.17 Hz and J(alpha beta) = 15.82 +/- 0.23 Hz were obt ained, while the values in calf muscle were J(gamma beta) = 17.16 +/- 0.12 Hz and J(alpha beta) = 16.04 +/- 0.09 Hz, The difference in J(gam ma beta) was significant. According to the literature, a possible reas on for greater ATP J coupling constants is a smaller fraction of ATP c omplexed to magnesium. However, the chemical-shift difference between alpha- and beta-ATP, which is also a measure for the fraction of ATP c omplexed to magnesium, showed only a small difference in ATP complexat ion: 88% in myocardium and 90% in calf muscle, This small difference c annot account for the observed difference in J gamma beta. (C) 1996 Ac ademic Press, Inc.