Effect of Repeated Doses of External and Internal Irradiation on Structure of the Spleen.

Abstract

Minimal doses of internal irradiation (0.01 to 0.05 mc of radiocolloidal gold) induced marked congestive swelling of the spleen in C3H mice, beginning within 5-6 days and persisting for about 14 days. No significant effect on the size of the spleen could be obtained with 50 to 200 r of X-rays. Large doses of radiogold (2mc) as well as of X-rays (1200 r) caused shrinkage and partial atrophy of the spleen within 3 days, the effect of the former being more severe. A large dose of colloidal radiogold (2 mc) injd. 5 or 6 days after pretreatment with a minimal dose (0.01 mc) of the same radioisotope induced within 3 days more marked shrinkage and more complete atrophy of the spleen than the same dose of radiogold without pretreatment. Substitution of radiogold (either of a preparative dose or of a large dose) by analogous doses of external irradiation did not reproduce the same drastic changes in the spleen. These findings were interpreted in the light of the existing evidence that the radiosensitivity of the spleen increases with increase of the blood supply. It was presumed that congestion of the spleen induced by a small dose of colloidal radiogold constituted "the preparative factor" responsible for potentiation of the effect of a subsequent injn. of a high dose of radiogold.