CRYOPRESERVATION OF RAT AND MONKEY LIVER SLICES

A method for the long-term storage of liver slices by cryopreservation was developed. The viability of liver slices was determined by analys ing the leakage of alanine aminotransferase, urea production, and the metabolism of testosterone. Rat liver slice; were found to be optimall y cryopreserved by exposure for 30 minutes to 12% dimethyl sulphoxide (v/v) at 2 degrees C before freezing. Subsequent direct immersion in l iquid nitrogen was more effective than a cooling rate of +/-1 degrees C/minute, which reduced viability. Storage at a temperature of -80 deg rees C lowered viability compared to storage at -196 degrees C. These conditions for optimal cryopreservation were used to cryopreserve rat, rhesus monkey and cynomolgus monkey liver slices. The viability of th ese liver slices was maintained at: 74%, 86% and 85%, respectively, wh en alanine aminotransferase content was measured; 80%, 109% and 82%, r espectively, when urea production was measured; and 109%, 60% and 85%, respectively, when the metabolism of testosterone was measured. Viabi lity was maintained for at least one month. The results show that, by using the method presented here, liver slices from these species can b e stored while maintaining viabilities similar to initial values. This method will facilitate the optimal use of liver slices and reduce the number of experimental animals used.