Chemical and Functional Correlates of Postischemic Renal ATP Levels

Renal energy metabolism was investigated before, during, and after ischemic insults of varying durations with in vivo 31P NMR spectroscopy. The postischemic recovery of renal ATP was found to be a biphasic process regardless of the length of the ischemia. This two-stage recovery consisted of a quick initial component immediately upon reflow followed by a slower, more gradual return toward preischemic levels. To characterize the source of each phase of the recovery, kidneys were extracted with perchloric acid at the end of the different periods of ischemia (before reflow). Concentrations of adenine nucleotides and breakdown products adenosine, inosine, and hypoxanthine were determined by 1H NMR spectroscopy. Excellent correlation was found between the residual nucleotide pool and the magnitude of the initial phase of ATP recovery. Additionally, the renal ATP content after 120 min of reflow was shown to have a strong correlation with subsequent functional recovery. These experiments show that in vivo 31P NMR can provide new and dynamic information concerning the biochemical recovery from ischemia. Furthermore, this data has the potential to predict the eventual functional recovery of the organ.