“…31 P-NMR spectroscopy is a sensitive, noninvasive probe of oxygen transport to, and the bioenergetic status of, cells, tissues, and organs (1, 2, 6, 7, 9, 12-16, 19, 20) that measures the amounts of compounds [phosphocreatine (PCr), P i , and nucleotide triphosphates (mainly ATP)] involved in oxidative energy metabolism in tissues. For example, P i is the low-energy degradation product of phosphorus metabolism that accumulates during hypoxia or ischemia (2,6,12,13,19).…”