X Irradiation of the Hypophysectomized Rat

Abstract

Sixty rats each received total-body X radiation in a single exposure (750 r.; 200 kv; dose rate, 18 r./min.); 30 rats were hypophysectomized 1 wk. prior to irradiation. The animals were exposed in groups of 10, each group containing equal numbers of intact and hypophysectomized rats. Animals were sacrificed 3 hrs. and 4 days after irradiation, and the adrenals, spleen, thymus, and left kidney were removed and weighed. Total adrenal cholesterol was detd. Nonirradia-ted controls were also sacrificed. The adrenal response to X irradiation was prevented by hypophysectomy. Changes in adrenal cholesterol and adrenal wt. at 3 hrs. and 4 days were not statistically significant. The terminal adrenal changes seen in intact animals were not seen in 2 hypophysectomized irradiated rats sacrificed in a moribund condition. Pituitary ablation did not alter the degree or time course of the splenic and thymic involution resulting from irradiation. Kidney, which was weighed as a control, did not change appreciably in either group after irradiation. Hypophysectomy appeared to potentiate X-ray toxicity. Nine of 20 hypophysectomized irradiated rats died 3-4 days after the exposure, whereas no intact irradiated animal died at this time. There were no deaths in the nonirradiated hypophysectomized group. Adrenal atrophy was evident in the hypophysectomized group at the time of irradiation, 7 days after the operation. At this time the cholesterol concn. in the gland was increased above that in the intact rat. However, the total cholesterol content of the adrenals was almost equivalent in both groups. Adrenal wt. was decreased still more and the cholesterol concn. was reduced in the rats killed 11 and 15 days after the operation. Hypophysectomy done 1 wk. prior to irradiation prevents the adrenal changes resulting from exposure to X-rays.