Sensitization of thermotolerant SCK cells to hyperthermia and freezing with reduction of intracellular pH: implications for cryosurgery.
OBJECTIVE
During cryosurgery, cells frozen slowly at the outer part of the ice ball undergo severe dehydration and are subject to solute effects injury, which may be caused in part by protein denaturation. This study was undertaken to determine whether heat shock proteins (HSPs), the molecular chaperones that stabilize proteins against denaturation, have a protective effect on cells during slow freezing. In addition, we aimed to determine whether acidic conditions, similar to those found in many solid tumors, would effect this protection.


METHODS
SCK cells were frozen at 5 degrees C/min to -10 degrees C or -20 degrees C before or after induction of thermotolerance, and at neutral or low pH conditions. Lethal damage was determined by clonogenics.


RESULTS
Clonogenic survival was decreased by 50% in thermotolerant cells frozen to -10 degrees C after culture in acidic conditions (pH 6.6) compared with non-thermotolerant cells cultured at neutral pH. Induction of thermotolerance alone or low pH alone did not significantly sensitize SCK cells to freezing. All treatment groups were equally susceptible to killing when frozen to -20 degrees C.


CONCLUSIONS
Our results show that induction of thermal tolerance does not protect SCK cells against subsequent freezing injury and that a low pH environment actually sensitizes these cells to freeze injury.
Burgher
Abram H
AH
Department of Urologic Surgery, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Swanlund
David J
DJ
Griffin
Robert J
RJ
Song
Chang W
CW
Bischof
John C
JC
Roberts
Kenneth P
KP
D000818:Animals; D002470:Cell Survival; D003452:Cryosurgery; D005260:Female; D005615:Freezing; D006360:Heat-Shock Proteins / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D015674:Mammary Neoplasms, Animal / Q000473:pathology*; D051379:Mice; D014407:Tumor Cells, Cultured
D006360:Heat-Shock Proteins