Fig. 2.

Typical examples of ³¹P-MRS spectra of an isolated rat heart, a while the heart is submerged in buffer and b after removing the effluent. The signal of the three phosphate groups of ATP, phosphocreatine (PCr), phenylphosphonate (PPA) as extracellular space marker, methylphosphonate (MPA), a solution in a small glass capillary as a reference, and dimethyl methylphosphonate (DMMP) as a marker of total water space are pointed out. MPA reference volume in (b) was different from that in (a)