TRANSPORT PHENOMENA DURING FREEZING OF ISOLATED HEPATOCYTES

The cellular response of isolated rat hepatocytes to freezing stress under various chemical and physical conditions was investigated using cryomicroscopic observations and a theoretical transport model. Cryomicroscopy was used to determine the cellular dehydration during freezing at different cooling rates. Using these results, water permeability parameters were also obtained. In addition, intracellular ice formation (IIF) parameters were obtained from rapid freezing experiments at a cooling rate of 400-degrees-C/min to decouple the effects of dehydration from IIF. The water permeability and IIF parameters were then used in a transport model to predict the probability of IIF under a wide range of chemical and physical conditions observed during cell freezing. In order to verify the model predictions, experiments were performed under similar conditions and compared to the theoretical predictions. The results suggest that slowly cooled cells ( < 80-degrees-C/min) dehydrate excessively and escape IIF. On the other hand rapidly cooled cells ( > 120-degrees-C/min) contain enough undercooled cellular water which undergoes IIF between -5 and -12-degrees-C.