INITIAL X-RAY EFFECTS ON THE AORTIC WALL 



209 



experiments in a dark room. The results are shown in Fig. 6. Irradiation of the 

 intimal membrane with 1,000 r at once caused a much more rapid permeation. 

 This result encouraged us to examine a possibly analogous radiation 

 effect m vivo. If a 1% solution of Congo-red in 5% glucose is injected intrave- 

 nously in a rat directly after a whole-body irradiation with 1,000-3,000 r 

 and the rat is killed 30 minutes later, the aorta is distinctly more stained than 



0-015 - 



0-010 



E 





0-005 



40 60 80 

 Time (min) 



Fig. 6. Rate of haematoporplij'rin diffusion through the intimal membrane of a pig's aorta, 

 before and after irradiation with 1,000 r. 



the aortae of non- irradiated control animals (as may be seen in Fig. 7). To 

 prevent confusion, caused by possible staining of the deeper aortic layers 

 through diffusion of dye from the vasal vessels, we modified the procedure. 

 After the aorta is excised, it is opened by a longitudinal cut at the dorsal side 

 between the origins of the intercostal branches. Then a thin intimal membrane 

 can be peeled off, which is put on a slide and dried. Immersion of this mem- 

 brane in glycerol makes it quite transparent and spectrophotometric estima- 

 tion of dye diffusion is possible. An example of such an estimation is shown in 

 Fig. 8. Here haematoporphyrin was used as the injected dye and the rats had 

 been exposed to 3,000 r. 



With regard to a possible chemoprotection against this vascular damage 

 by ionizing radiation I might say that in our work NagSaOg (sodium 

 thiosulphate) has given some very promising results. In all of the radiation 

 effects on mucopolysaccharide systems we have studied, the vascular effects 

 included, NagSaOg acts as an efficient protector (Fig. 9). Intracellular radia- 

 tion effects are not influenced by thiosulphate (the LD^q^ 30 days for C57 

 black mice does not change), but there might be considerable j^rotection 

 against the extracellular radiation effects on vascular walls. The toxicity of 



