Cellular tolerance to pulsed hyperthermia

Transient heating of tissues leading to cellular stress or death is very common in medicine and biology. In procedures involving a mild (below 700.2em0ex^∘C) and prolonged (minutes) heating, such as hyperthermal tumor therapy, the cellular response to thermal stress is relatively well studied. However, there is practically no data on cell viability at higher temperatures and shorter exposures, while the demand for this knowledge is growing. Two main reasons motivate this research: (i) a growing number of laser therapies and surgical procedures involving pulsed heating, and (ii) cellular viability data at short exposures to high temperatures provide a unique insight into the understanding of processes leading to thermally induced cellular death. We designed a technique and performed a study of cell viability under pulses of heat from 0.30.3em0exto0.3em0ex1000.3em0exms in duration with peak temperatures as high as 1300.2em0ex^∘C. We found that the threshold of cellular death in this range can be accurately approximated by the Arrhenius law with the activation energy of 10.3em0exeV, a significantly lower value than was reported in studies based on multisecond exposures.