Experimental studies of thermotolerance in vivo. I. The baby rat tail model.

Abstract

A detailed study of the kinetics and magnitude of thermotolerance has been made using the endpoint of loss of vertebrae in the baby rat tail. A range of different priming treatments was used and for analysis each priming treatment (PT) was given in terms of the heat sensitivity of the tissue as defined by the single treatment (Ds) required for a given effect, i.e. fractional priming treatment PT/Ds. A considerable degree of thermotolerance could be induced so that at maximum the tissue sensitivity was reduced by a factor of more than four in heating time to produce a given effect, or by more than the equivalent of 2 degrees C. The main results of the study were: (a) that the time to reach maximum thermotolerance depends primarily on PT/Ds, independent of the particular conditions used in the priming treatment; (b) that the extent of the maximum also depends primarily on PT/Ds, but the precise form of the relationship depends on the method used to define thermotolerance; and (c) that the rate of decay of thermotolerance is independent of the priming treatment. The implications of these results for clinical hyperthermia are briefly discussed.