Choline Uptake into Renal Phospholipids following Renal Ischemia in Rats

SUMMARY Renal phospholipid metabolism was studied after ischemia was induced by occlusion of the left renal artery in the rat. There was no change in the rate of cellular ["C]choline uptake after 25 or 80 minutes of ischemia. However, [uC]choline incorporation into phospholipid was two to three times greater in slices from the ischemic kidney than in slices from the contralateral control kidney. The increase occurred after 25 minutes of ischemia plus 15 minutes of reflow, and after 60 minutes of ischemia with or without reflow. When [uC]choline was injected into rats after a 60-minute period of renal ischemia, the rate of incorporation into phospholipid in the ischemic kidney was almost twice that of the control kidney. These results were similar to those of the in vitro experiments. Since virtually all of the cellular phospholipids of the kidney are present in cellular membranes, renal ischemia affects membrane metabolism. The mean distribution ratio of a-aminoisobutyric acid in slices of kidneys ischemic for 60 minutes was similar to that of control slices: 4.11 ± 0.2 (SEM) VS. 4.30 ± 0.30. The normal uptake of a-aminoisobutyric acid indicates that the increased incorporation of choline is associated with functional integrity of the membrane. Ore Reg 44: 62-67, 1979 DAMAGE to cell membranes is a prominent fea-ture of renal ischemia. In rats, after occlusion of the renal artery for periods up to 1 hour, the damage is especially evident in the proximal tubular cells, which become denuded of brush border membranes (Reimer and Jennings, 1971a; Reimer et al., 1972; Venkatachalam et al., 1978). If the ischemic period is short, the membranes regenerate; with longer periods of ischemia, cellular necrosis ensues. Phos-pholipids are the basic structural component of cellular membranes. We therefore investigated membrane metabolism in renal ischemia by deter-mining the rate of incorporation of [uC]choline into phospholipid of ischemic rat kidneys. We also de-termined the transport of a-aminoisobutyric acid (AIB) in the kidneys, since the membrane damage might be expected to affect the membrane transport of metabolites