THE WEIGHT OF LYMPHOID ORGANS AND THEIR RESPONSE TO ACTH FOLLOWING THYMECTOMY IN THE RAT

Abstract

SUMMARY Thymectomized rats and their control-operated litter-mates received adrenocorticotrophic hormone (ACTH; 4 i.u./day for 10 days) or control injections. Thymectomy had no effect upon body weight under either treatment. In rats injected with ACTH, the weight of lymph nodes was lower in thymectomized than in control-operated animals (P < 0·001 for the nodes of certain regions). A reduction in weight of lymph nodes following thymectomy also occurred in rats receiving control injections but, in this case, the difference was of doubtful significance. Under treatment with ACTH, the adrenals of thymectomized male rats weighed more than those of control-operated animals; this difference was significant only at the 2% level of probability. In female rats receiving ACTH, and in control-injected rats of both sexes, thymectomy had no effect upon adrenal weight. The possibility that the results were due to non-specific stress following thymectomy is discussed, and evidence against this explanation is presented.