Effects of hyperthermia on the colony-stimulating factor production by the lung☆

Abstract Hyperthermic treatment of the murine lung in the range of 40–46°C inhibited the production of colony-stimulating factors by the lung in vitro . This inhibition was dose dependent. Thermodynamic analysis was used to determine the activation energies. The Arrhenius plot contained a transition at 43°C. At temperatures below and above the transition temperature, the activation energies were 40.49 and 197 kcal/mole, respectively. Below the transition temperature, the effect of hyperthermia was characterized by a delayed response represented by the broad, initial shoulder of the hyperthermic dose-response curves. To investigate the mechanism of hyperthermia-induced reduction of the colony-stimulating factor production, the effect of hyperthermia on the protein synthesis by the lung was also studied. The results indicated an immediate response to hyperthermia, characterized by the absence) of the initial shoulder and the high slope of the hyperthermic dose response curves. The corresponding Arrhenius plot did not have any transition point. The single activation energy calculated was 97.25 kcal/mole. It is concluded that the hyperthermic depression of the colony-stimulating factor production by the lung cannot be explained solely on the basis of the effects of hyperthermia on the protein synthesis.