31P nuclear magnetic resonance and saturation transfer studies of the isolated perfused rat kidney

Previous studies using 31P nuclear magnetic resonance (NMR) saturation transfer techniques to quantitate the energy metabolism of the kidney have often resulted in estimates of adenosine triphosphate (ATP) turnover which are much lower than those predicted from the renal oxygen consumption and reasonable values of the P/O ratio. We measured the ATP turnover in isolated perfused kidneys of rats, using 31P NMR saturation transfer and a new procedure for quantitation of the intracellular Pi concentration. The estimated turnover rates of ATP were higher than previously reported. The P/O ratios calculated on the basis of these rates of ATP turnover and rates of renal oxygen consumption reported in the literature were within the range of theoretically possible values. Thus, 31P NMR saturation transfer can be used to quantitate the ATP turnover in the isolated perfused rat kidney.