Preservation of freshly isolated liver cells in liquid nitrogen at -196 degrees C.

Rat-liver cells obtained through perfusion and collagenase treatment were frozen according to a fixed schedule and stored in liquid nitrogen at -196 degrees C. The metabolic capacity of the cells after thawing was tested by measuring their ability to achieve metabolic activation of cyclophosphamide, which in turn was measured as induction of sister-chromatid exchanges in human lymphocytes. The viability and metabolic efficiency of the frozen and thawed cells were comparable with those of fresh cells.