The Effect of Environmental Factors on the Radio-sensitivity of Lymph Nodes Cultured<i>in vitro</i>

Abstract

Rat lymph nodes were cultured in vitro in a serum-saline medium. The radiosensitivity of the lymphocytes was assessed by determining the percentage which were pyknotic (dead) five hours after exposure of the cultures to standard doses of X rays. The effect of various environmental factors on radiosensitivity was investigated by altering the composition of the culture medium before irradiation. It was found that sensitivity increased linearly with the concentration of dissolved oxygen over the range 0–22 ml O2/litre, the increase in sensitivity over this range being twelvefold. CO2 over the range 0–7 per cent in the gas phase, and glucose over the range 0·1–0·6 per cent, had no effect. Change of pH from 7·0 to 8·4 had no effect, but sensitivity appeared to decrease considerably at pH 6·3 and greatly at pH 6·0, though the interpretation of this result is uncertain. Lactate, 0·02 M., decreased sensitivity by a factor of 1·7. In “physiological saline” sensitivity was the same as in serum medium, and it was concluded that none of the organic constituents of serum influenced radiosensitivity at ordinary concentration levels.