Abstract
Step-down heating (SDH) was investigated in mouse testis by giving an initial treatment of 3 min at 43.0°C followed immediately by a treatment in the temperature range 38.0–42.0°C. The dose-response curves for testis weight loss as a function of duration of hyperthermia were compared with those obtained using single-temperature treatments. In all cases the curves were linear, allowing the use of Arrhenius analysis. For single- temperature treatments the Arrhenius relationship showed an inflection at approximately 41°C with a small, but significant, increase in activation energy for hyperthermal temperatures below the transition. SDH increased the thermal sensitivity in this lower range, by approximately 1 °C, but the activation energy was not significantly altered. The results support the view that in vivo thermosensitization by SDH is not due solely to inhibition of development of thermotolerance.
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