The Effects of Localized Cathode-Ray Particle Irradiation of the Hypophysis and Whole-Body X-Irradiation on Gonadotrophin, Thyrotrophin, and Adrenocorticotrophin of the Rat Pituitary

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Abstract
Gonad stimulating hormone (GSH), thyroid stimulating hormone (TSH), and ACTH, were bioassayed 1, 6, and 24 hours (hr.) post-irradiation in intact, sham irradiated, whole-body irradiated, leg irradiated, and head shielded irradiated rats. Localized (2 Mev Van de Graaff, 1100 kv, 104 rep to 0.0069 cm3 of pituitary tissue) irradiation andwhole-body irradiation (250 kv, 30 ma, 0.25 Cu, 1 mm Al, 50 cm distance, 1000 r) were used. Both operative manipulation and irradiation caused a decrease in GSH. In hypophyseally irradiated rats there was a precipitous drop at 1 hr. which remained significantly low for 24 hr. In whole-body irradiated animals the decrease was at 6. and 74-hr, post-irradiation. Levels of TSH of sham-irradiated, head shielded, and whole-body irradiated rats 1-hr. post-irradiation were similar to intact controls. A highly significant augmentation in TSH occurred 1 and 6 hr. after pituitary exposure, but dropped to subnormal levels in 24 hr. At 6 and 24 hr. after whole-body irradiation a similar significant increase in TSH occurred. In hypophyseally irradiated rats the ACTH was significantly higher for all points on the time curve. In contrast, whole-body irradiation caused a rise at 1 hr. which fell to control levels at 6 hr. and below normal at 24 hr. Head shielded animals showed an increase in ACTH at 1-hr. post-irradiation similar to that of pituitary irradiated animals. Shielding of the head and neck, although it does not prevent hormonal changes, is of protective value, since it delays for at least 48 hr. the lethal effects of radiation (8000 r). Of special interest is the fact that irradiation of 0.0069 cm3 of pituitary is lethal within 24 to 48 hrs. It is concluded, from the distinctive hormonal patterns elicited by the radiations, and the rapid lethality of direct hypophyseal irradiation, that the anterior lobe of the rat is a remarkably radioresponsive tissue.