PHYSIOLOGY OF RADIATION INJURY 991 



animals, whereas cholesterol concentration increases after hormonal 

 stimulation of several days duration (Sayers et al., 1944). The rise in 

 adrenal cholesterol occurring several days after median lethal irradiation 

 may represent over-stimulation in excess of cortical hormone demand 

 (Patt et al., 1947). That the elevated cholesterol is not a result of 

 adrenal exhaustion is suggested by its absence with higher dosages. 

 Although adrenal lipids are usually depleted before death, it is not known 

 whether this is a cause or an effect of the terminal events. The possi- 

 bility exists that direct injury of the gland decreases its capacity to 

 respond to the stress of irradiation, since some protection has been 

 observed in rats when the adrenals are shielded during exposure (Craver, 

 1948; Edelmann, 1951a). Moderate degrees of stress (KC1 and hista- 

 mine) are well tolerated by the mouse after minimally lethal irradiation 

 (W. W. Smith, 1951). 



There are a few indications of altered medullary activity. However, 

 the results are not particularly impressive. An initial discharge of 

 epinephrine may be anticipated with irradiation of large areas of the 

 body, but this has not been proved. Irradiation of the dog's adrenal 

 is said to increase the pressor action of blood collected from the adrenal 

 vein (Zunz and La Barre, 1927). On the other hand, significant changes 

 in adrenal catechols, which include epinephrine, have not been observed 

 after exposure of the rat adrenal to 100 or 1000 r (Raab and Soule, 1927). 

 Therapeutic irradiation apparently prevents increased output of medul- 

 lary hormone after exercise in patients with angina pectoris (Raab, 1941). 

 Reports of a salutary effect of adrenal irradiation in hypertension are 

 controversial (Torgersen, 1940). 



The adrenals are implicated in some of the remote and indirect effects 

 of irradiation. Generalized involution of lymphoid structures has been 

 described following heavy local irradiation (Leblond and Segal, 1942; 

 Halberstaedter and Ickowicz, 1947). After adrenalectomy, the changes 

 are restricted to the irradiated area. The picture following total-body 

 exposure is somewhat obscure, although there is general agreement that 

 lymphoid involution after moderate dosages does not require the adrenal 

 or pituitary for its development (Dougherty and White, 1946; Patt et al., 

 1948). Involution of lymphoid tissues and augmentation of antibody 

 titer subsequent to total-body exposure to 10 r have been attributed to 

 the adrenal (Dougherty and White, 1946; Dougherty et al, 1944); the 

 indirect action of a minimal lymphopenic dose and the "anamnestic 

 response" of antibody titer are not well substantiated, however (Crad- 

 dock and Lawrence, 1948; Marder et al., 1948). 



The toxic reaction resulting from irradiation of large portions of the 

 body is potentiated in the absence of the adrenals or pituitary (Leblond 

 and Segal, 1942; Cronkite and Chapman, 1950; Edelmann, 1951b; Kaplan 

 et al., 1951; Patt et al., 1948). Susceptibility of adrenalectomized mice 



