31P relaxation rates to evaluate physiological events in the heart.

The present study was performed to determine whether 31P NMR relaxation times (T1) of adenosine triphosphate (ATP) might be used to monitor the resultant altered myocardial physiology produced by ischemia and possibly to explain mechanisms of altered physiology. To this end, pre- and postischemic T1s were determined in hearts perfused in the Langendorff mode, using 31P NMR inversion recovery methods. In hearts without any pretreatment (CON), post-ischemic ATP T1 values were significantly decreased compared with pre-ischemic values (P < 0.05); Pre-isch: gamma = 0.58 +/- 0.08; alpha = 0.62 +/- 0.06; beta = 0.38 +/- 0.08; Post-isch: gamma = 0.33 +/- 0.05; alpha = 0.43 +/- 0.03; beta = 0.23 +/- 0.05. In groups pretreated with creatine (CR), cyclocreatine (CY), or superoxide dismutase plus catalase (SOD-CAT) before ischemia, the post-ischemic ATP T1 values were similar and were not significantly changed from pre-ischemic values. These combined data suggest that T1s of ATP might be used to monitor altered myocardial physiology and could provide insight into mechanisms of alteration.