↵1-a  Viability was measured by trypan blue exclusion assay immediately after thawing the cells and after a Percoll gradient to remove the dead or damaged cells, as described under Materials and Methods. Recovery was defined as the percentage of cells left relative to the number of cells initially cryopreserved. Data are expressed as mean ± SEM. There was no significant difference in cell survival immediately after thawing, but there was a significant difference according to thet test (P < 0.05; n = 6) (

↵1-150 ) between the two cryopreservation methods after the Percoll step.

↵1-b  Isolated rat hepatocytes were cryopreserved following two different protocols: Method 1 referred to 1 h at −20°C then 1 h at −70°C, and Method 2 referred to use of the Forma Scientific freezer as described underMaterials and Methods.