Radiosensitivity of Skin of New-Born Rats. III. Sensitivity at Different Temperatures. ∗

In a previous paper 1 it has been reported that temperatures of 0-5°C during roentgen irradiation (1,300 r) decreased the amount of injury produced in the skin of new-born rats. In a second series of experiments 2 this increased resistance of animals irradiated at 0-5°C was studied quantitatively for dosages ranging from 300 to 3000 roentgens. The purpose of this investigation was to determine whether the resistance would change quantitatively with increasing temperature.

The animals were of the same strain used in the previous studies.† The temperature was controlled during the irradiation by placing the animals in a double walled box, constructed of transparent sheet plastic, containing water at the desired temperature. The temperature of the skin before and after the irradiation was determined by means of a thermocouple. Experiments indicated that the rectal temperature changed very rapidly to that of the skin at low and at high temperatures, but at room temperature the interior of the body was slightly warmer than the skin.

The radiation used was unfiltered except for 1 mm of cardboard and 2 sheets of 0.5 mm plastic. The radiation was delivered at 130 K.V. peak and 5 ma. The half-value layer was ca. 1.5 mm aluminum. The intensity in the box at 26°C was 137 roentgens per minute. The target distance was 30 cm.

The exposed skin was a 6 × 9 mm area to one side of the mid-ventral region of the abdomen. Both ventral and dorsal skins were examined microscopically 2 weeks later, and the extent of injury determined in units as described in a previous report. 2

Fig. 1 shows some typical results of irradiation at different temperatures. These animals were litter mates and each was given the same dosage.