Membrane damage occurs during the formation of intracellular ice.

Current theories on both the formation of intracellular ice (IIF) and the mechanisms by which it damages cells all implicate the plasma membrane. While it has been well documented that following IIF post-thaw damage to the plasma membrane occurs, it is not known whether this damage occurs during freezing or thawing. By directly monitoring the diffusion of a membrane-impermeable fluorescent stain into V-79W fibroblasts, the integrity of the plasma membrane during freezing and thawing was correlated with the incidence of IIF. While this study presents evidence that membrane damage occurs during the formation of intracellular ice in cell suspensions, single attached cells and confluent monolayers, we cannot conclude whether IIF is the cause or result of membrane damage.