The effect of cooling and warming rate on cortical cell function of glycerolized rabbit kidneys

Experiments previously reported (I.A. Jacobsen, D.E. Pegg, H. Starklint, J. Chemnitz, C.J. Hunt, P. Barfort, and M.P. Diaper, Cryobiology 19, 668, 1982) suggested that rabbit kidneys permeated with 2 M glycerol are least damaged during freezing and thawing if they are cooled very slowly (1 degree C/hr). Using similar techniques of glycerolization, cooling, storage at -80 degrees C, rewarming, and deglycerolization, active cell function in cortical tissue slices prepared from such kidneys has now been studied. Oxygen uptake, tissue K+/Na+ ratio after incubation, and slice/medium PAH ratio after incubation were measured. Kidneys cooled at 3.1 degree C/min and warmed at 4.2 degrees C/min gave poor results in the previous studies and the lowest levels of cell function in the present experiments. Kidneys cooled at 1 degree C/hr exhibited degrees of slice function that were dependent on warming rate: warming at 1 degree C/min was better than warming at either 1 degree C/hr or c.20 degrees C/min. These results refine the previously drawn conclusions, (loc cit) and indicate optimal cooling and warming rates for rabbit kidneys containing 2 M glycerol, in the region of 1 degree C/hr cooling and 1 degree C/min warming. These rates are much lower than have hitherto been used by others for any system. Some implications of these findings are discussed.