Thermosensitization by step-down heating in mouse testis

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.

Key Words:

• testis
• hyperthermia
• step-down heating.