Rapid cold-hardening increases membrane Xuidity and cold

The rapid cold-hardening (RCH) response not only confers dramatic protection against cold-shock (non-freezing) injury, but also “instantaneously” enhances organismal performance. Since cold-shock injury is associated with damage to the cell membrane, we investigated the relationship between RCH and changes in cold tolerance and membrane Xuidity at the cellular level. None of the adult Xies (Sarcophaga bullata) in the cold-shocked treatment group survived direct transfer to ¡8 °C for 2 h; in contrast, 64.5% of Xies in the RCH group survived exposure to ¡8 °C. DiVerences between the treatment groups also were reXected at the cellular level; only 21.3% of fat body cells in the cold-shocked group survived compared to 68.5% in the RCH group. Using 31P solid-state NMR spectroscopy, we determined that membrane Xuidity increased concurrently with rapid cold-hardening of fat body cells. This result suggests that membrane characteristics may be modiWed very rapidly to protect cells against cold-shock injury.  2006 Elsevier Inc. All rights reserved.