Abstract
An immediate effect of head X-irradiation on the hypo thalamic-pituitary-adrenal and -gonadal systems was investigated in adult male dogs. Under pentobarbital anesthesia, the animals were given 200-1, 000 R of X-irradiation to their heads. During a period of 125 minutes after ex-posure, adrenal and testicular venous blood samples were collected intermittently, and were analyzed for 17-hydroxycorticosteroids and 17-oxosteroids, respectively. After X-irradiation of 200 R, there was a subtle decrease in the secretory activity of the adrenal cortex, but it returned to pre-radiation levels by 30 minutes. Exposure to doses of 500 R was accompanied by a rapid and temporary stimula-tion of the adrenal cortex and its effect lasted for approximately 60-90 minutes. At doses of 1, 000 R, there was an initial decrease in adrenocortical secretion followed by an appreciable increase within approximately 30-60 minutes after irradiation. However, head X-irradiation with doses of 200-1, 000 R failed to produce a notable increase in the secretory activity of the testis. It is thus suggested that exposure of the head to 500-1, 000 R of X-rays can elicit a rapid and temporary activation of the hypothalamic-pituitary-adrenal axis during the immediate period after irradiation but it does not exhibit any activity in the hypothalamic-pituitary-gonadal axis. -head X-irradiation; adrenal 17-hydroxycorticosteroid secretion; testicular 17-oxosteroid secretion; hypo-thalamic-pituitary-adrenal axis; hypothalamic-pituitary-gonadal axis; dog
