APPLICATION OF MAGNETIC-FIELD-INDUCED HEAT-SHOCK-PROTEIN-70 FOR PRESURGICAL CYTOPROTECTION

To develop an alternative to hyperthermia for the induction of hsp70 f or presurgical cytoprotection, we investigated the optimal exposure co nditions for magnetic field induction of hsp70. Normal human breast ce lls (HTB124) were exposed to 60-Hz magnetic fields and hsp70 levels we re measured following three different exposure conditions: continuous exposure up to 3 h, a single 20-min exposure, and a single 20-min expo sure followed by repeated 20-min exposures at different field strength s. In cells exposed continuously for 3 h, hsp70 levels peaked (46%) wi thin 20 min and returned to control levels by 2 h. Following a single 20-min exposure, the return of hsp70 levels to control values extended to more than 3 h. When cells underwent a 20-min exposure followed by repeated 20-min exposures (restimulation) with different field strengt hs, additional increases in hsp70 levels were induced: 31% at 1 h, 41% at 2 h, and 30% at 3 h. (C) 1998 Wiley-Liss, Inc.