pH was maintained between 7.2 and 7.4. Claes used a perfusate based on human albumin (Kabi: Sweden) diluted with saline to a concentration of 45 g/L. Claes preserved 4 out of 5 dog kidneys for 96 hours with the kidneys functioning immediately after reimplantation despite immediate contralateral nephrectomies. Claes also compared this perfusate with Belzer's cryoprecipitated plasma in a control group and found no significant difference between the function of the reimplanted kidneys in the two groups. The only other group besides Woods' to report successful seven-day storage of kidneys was Liu and Humphries in 1973. They had three out of seven dogs surviving, after their kidneys had been stored for seven days followed by reimplantation and immediate contralateral nephrectomy. Their best dog had a peak post reimplantation creatinine of 50 mg/L (0.44 mmol/L). Liu used well hydrated dogs undergoing a mannitol diuresis and stored the kidneys at 9 °C – 10 °C using a perfusate derived from human PPF. The PPF was further fractionated by using a highly water-soluble polymer (Pluronic F-38), and sodium acetyl tryptophanate and sodium caprylate were added to the PPF as stabilisers to permit pasteurisation. To this solution were added human albumin, heparin, mannitol, glucose, magnesium sulphate, potassium chloride, insulin, methyl prednisolone, carbenicillin, and water to adjust the osmolality to 300-310 mosmol/kg. The perfusate was exchanged after 3.5 days storage. Perfusate pressure was 60 mm Hg or less, at a pump rate of 60 per minute. Perfusate pH was 7.12–7.32 (at 37 °C), Pco2 27–47 mm Hg, and Po2 173–219 mm Hg. In a further report on this study Humphries found that when the experiments were repeated with a new batch of PPF no survivors were obtained, and histology of the survivors from the original experiment showed glomerular hypercellularity which he attributed to a possible toxic effect of the Pluronic polymer. Joyce and Proctor reported the successful use of a simple dextran based perfusate for 72-hour storage of dog kidneys. 10 out of 17 kidneys were viable after reimplantation and immediate contralateral nephrectomy. Joyce used non pulsatile perfusion at 4 °C with a perfusate containing Dextran 70 (Pharmacia) 2.1%, with additional electrolytes, glucose (19.5 g/L), procaine and hydrocortisone. The perfusate contained no plasma or plasma components. Perfusate pressure was only 30 cm H2O, pH 7.34-7.40 and Po2 250–400 mm Hg. This work showed that, for 72-hour storage, no nutrients other than glucose were needed, and