31P nuclear magnetic resonance study of the recovery characteristics of high energy phosphate compounds and intracellular pH after global ischaemia in the perfused guinea-pig heart.

The recovery of high energy phosphate compounds in perfused guinea-pig heart at 20 degrees C after a 12 min period of global ischaemia was examined using 31P-NMR with a time resolution of 12 s. This time resolution was achieved by overlaying the data acquired from five successive ischaemic periods by arresting and restoring the flow of perfusion fluid to the heart in synchrony with the data acquisition sequence. The rate of creatine phosphate resynthesis after the ischaemic period proceeded 14 times faster than its rate of loss during the ischaemic period. ATP levels did not decrease during ischaemia and ADP was undetectable at any time. Estimates of intracellular pH from the chemical shift of the inorganic phosphate peak were impossible in normal guinea-pigs since the inorganic phosphate peak was not clearly defined. During the ischaemic period the inorganic phosphate peak increased in size and shifted upfield. On restoration of flow, the inorganic phosphate peak collapsed in a complex way following a different path to its formation during ischaemia.