The influence of temperature on the function of renal cortical slices frozen in various cryoprotectants

Renal cortical slices were frozen to various subzero temperatures after treatment with 2.1 M of one of three cryoprotectants, dimethyl sulfoxide (Me2SO), ethylene glycol, or glycerol. The effects on tissue [K+]/[Na+] of cooling to these temperatures were tested (using identical procedure times, cooling rates, and warming rates) by holding the slices at each experimental temperature for appropriate periods of time prior to rewarming. The effects of the holding time were assessed by comparison with slices which were cooled and rewarmed with no intermediate holding time. Slices treated with ethylene glycol or glycerol were found to exhibit a continuous decrease in [K+]/[Na+] with lowered temperatures, in contrast to those treated with Me2SO. Slices treated with Me2SO actually experienced a continuous increase in [K+]/[Na+] with lowered temperature (-12 to -33 degrees C). Me2SO does exhibit toxic effects at subzero temperatures. Adverse effects of holding time on viability are seen for Me2SO-treated slices at higher subzero temperatures. These effects were alleviated as the temperature is reduced, suggesting that temperature has a greater effect on survival of renal cortical tissue than Me2SO concentration. However, the toxicity observed at higher subzero temperatures is expected to be of importance, particularly for slowly cooled tissues which are exposed to these temperatures for relatively long periods of time.