The response of the rat tail to combined heat and x rays.

Moderate heat doses which, alone, cause no measurable response in the cartilage of the tail of the baby rat, may potentiate the effects of X-irradiation. The magnitude of the enhancement (the Thermal Enhancement Ratio, or TER) depends upon the heat dose in a similar way to that observed in other normal tissues. The thermal enhancement in the rat tail was also dependent on the dose of X rays, increasing with increasing dose. Potentiation was always greater when heat was applied before irradiation although the difference in TER between heating immediately before or after irradiation was less than 10%. Potentiation of X ray damage decreased steadily to zero as the heat and X-ray treatments were separated by increasing intervals of time. The loss of potentiation was more complete and more rapid when X rays were given before heating, but was also dependent on both the degree of heating and the dose of X rays.