PHYSIOLOGY OF RADIATION INJURY 975 



1949). Plasma turbidity is not apparent, however, in the irradiated rat, 

 although the total lipid content of plasma is elevated (Kohn, 1951a). 

 Plasma phospholipid may rise or remain unchanged (Kohn, 1951a; 

 Neve and Entenman, 1951), while plasma cholesterol is reported to 

 increase in guinea pigs, mice, rats, and dogs (Prosser, Painter, Lisco, 

 et al., 1947; Kohn, 1950, 1951a; Low-Beer, 1933). In the rat and guinea 

 pig cholesterol rises on the second or third day after acute irradiation and 

 returns to normal by the sixth day, the pattern resembling that of 

 chloride. In chronically irradiated dogs (50 r per day) cholesterol is 

 elevated only terminally. There are no significant changes in cholesterol 

 concentration with daily dosages of 10 r or less (Fink, 1946). Alteration 

 in the cholesterol content of serum and in the chylomicron count (mobile 

 visible plasma lipids) has been observed in patients receiving radiation 

 therapy. Several investigators have alluded to a relation between the 

 direction of cholesterol change and clinical radiation sickness; the latter 

 is not seen in patients whose serum cholesterol is elevated (Low-Beer, 

 1933; Hummel, 1930; Holmes, 1941). Reduction of the chylomicron 

 count also appears to be related temporally to radiation sickness and is 

 observed after irradiation of the abdomen or thorax but not of the 

 extremities (Setala and Ermala, 1948). 



A moderate increase in plasma alkaline phosphatase occurs in rats 

 24 hours after irradiation with dosages of 200 to 600 r (Ludewig and 

 Chanutin, 1950a). Enzyme activity decreases on the second day in 

 animals exposed to the higher dosage. Phosphatase activity in the rat is 

 also depressed by multiple small dosages of radiation. There is little 

 change in alkaline and acid phosphatases of plasma after chronic X 

 irradiation of dogs (Prosser and Moore, 1946; Fink, 1946). 



The sulfhydryl content of plasma is decreased in the rat about 5 days 

 after X irradiation with 750 r (Shacter, 1951); the significance of this 

 change is not understood. Similar effects have been observed after 

 nitrogen mustard poisoning and surgical trauma and appear to be related 

 chronologically to initiation of tissue regeneration. A fall in serum 

 ascorbic acid has also been reported in animals and man (Kretzschmar 

 and Ellis, 1947). The maximum decrease is seen about one week after 

 exposure. 



Plasma histamine is increased in the irradiated rat and rabbit (Painter 

 et al, 1947; Weber and Steggerda, 1949). In the rat given 600 r, two 

 peaks of histamine elevation are seen, the first two hours after exposure 

 and the second at five days (Weber and Steggerda, 1949). There is some 

 reason to believe that histamine liberated from damaged cells and perhaps 

 newly formed from irradiated histidine can account for certain of the 

 radiation effects (Ellinger, 1951). Other toxic materials may be present 

 in the plasma of irradiated animals, but these have not been identified 

 (Venters and Painter, 1950). 



