[Intrarenal energy metabolism in ischemic renal injury in rabbits]

In order to clarify the cause of the decrease in the urinary excretion of NAG (U-NAG) in severe ischemic renal injury in rabbits, we studied intrarenal energy metabolism in ischemic renal injury. After 5 min of ischemia, energy charge and ATP significantly decreased by 50% and 29% respectively. These parameters, however, did not significantly show the change in more than 5 min of renal ischemia. Energy charge and ATP did not reflect the degree of renal injury produced by ischemia, while it was indicated that the longer the period of ischemia until 120 min of ischemia, the less the rate of intrarenal ATP resynthesis at 30 min after reflow. Intrarenal lactate content increased significantly from the 5 min ischemia group to the 180 min. These results suggest that no improvement in intrarenal energy metabolism with increasing duration of renal ischemia is showed and ischemic renal injury develops progressively. It is probable that the decrease in U-NAG in severe ischemic renal injury is due to the inability of the kidney to wash out NAG into the urine, although NAG may be released from the injured tubular cells in proportion to ischemic renal injury. Therefore, in spite of severe ischemic renal injury, U-NAG may show low values, and may lead to misjudgement that the proximal tubular cells are intact. U-NAG should be measured repeatedly and estimated in association with the other renal function tests, especially creatinine clearance, for the correct evaluation of ischemic renal injury.