Effect of Hypophysectomy on Immunological Recovery after Sublethal Irradiation of Adult Rats

Abstract

Recent observations (1-6) have focused attention on a relationship of the anterior pituitary, the thymus, and the thymusdependent lymphoid system. It has been proposed that growth hormone mediates pituitary control of the thymus (2), but the possibility of a more specific thymotropic hormone has not been excluded.In order to gain more insight into the pituitary control of immunologic function, we have studied immunologic recovery after sublethal irradiation of young adult hypophysectomized rats. The results indicated that hypophysectomy interfered with immunologic recovery after total body irradiation.Materials and Methods. Male Wistar-Furth rats (A. R. Schmidt Co., Madison, Wisconsin), hypophysectomized at 8 weeks of age, were exposed to 500 R of total body irradiation at 10 weeks of age. Normal, irradiated, and hypophysectomized nonirradiated rats were included as controls. Because hypophysectomized rats do not tolerate low ambient temperatures, all rats were maintained at 84 t 2°F. They were fed Purina Rat Chow and given tap water ad libitum.Each rat was bled from the tail at 24 hr and again at 7 weeks after irradiation, and the peripheral white blood cell count was determined.

Immunodeficiency in Hypophysectomized Rats

“…The direct effect of various hormones on the immune system (Ambrose 1964;Cohen et al 1970;Duquesnoy et al 1969;Fabris et al 1971Fabris et al , , 1972Fabris 1973;Ahlqvist 1976;Pierpaoli 8c Sorkin 1972;Pierpaoli et al 1970;Sherman et al 1973) suggests that the pituitary gland influences immune reactions specifically via hormonal mechanisms, rather than through the non¬ specific effect of malnutrition. In fact it is quite conceivable that the immunoregulatory function of hormones hinges on lymphocytes which are known to play a key role in most, if not all, the immune reactions (Miller 1975).…”

“…Thyroxine, growth hormone and insulin seem to be needed for the ontogenic maturation (Fabris et al 1971«;Fabris 1973) and maintenance (Duquesnoy et al 1969;Fabris et al 1971Fabris et al «,b, 1972Fabris 1973;Pierpaoli 8c Sorkin 1972;Pierpaoli et al 1970) of the im¬ mune System. The immunosuppressive effect of adrenal steroids (White 1958) is well recognized, although small amounts of glucocorticoids are necessary for in vitro immune reactions (Ambrose 1964;Cohen et al 1970;Sherman et al 1973).…”

Effect of Growth Hormone on the Metabolism of Thymus and on the Immune Response Against Sheep Erythrocytes

“…• VOLUME 134, 1971 1095 GROWTH HORMONE ACTION ON THY3gUS irradiated, hypophysectomized animals, there is deficient recovery of total leukocyte counts, hemagglutination titers to SRBC, and skin allograft rejection. Suggestions have been made for the possible presence of a thymotropic hormone in the pituitary (21).…”