INITIAL X-KAY EFFECTS ON THE AORTIC WALL AND 

 THEIR LATE CONSEQUENCES 



H. B. LAMBERTS 



Physiologisch Laboratorium, der Rijksuniversiteit, Groningen, Holland 



SUMMARY 



Effects of X-irradiation in vivo and in vitro on the aortic wall are described, e.g. increased 

 atheromatosis in hypercholesterolaemic rabbits drop of injection-pressure in the aortic wall 

 and increased permeability for several dyes. The importance of the radiosensitivity of 

 the mucopolysaccharide matrix is stressed. The possibility of chemical protection of this 

 matrix by NagSjOg (sodium thiosulphate) is discussed. 



In considering late vascular damage by irradiation we can start with the 

 statement that no doubt is accurate about the end effect: a single aortic 

 irradiation in dogs with 1,500-2,500 r wiU cause atherosclerosis in 30 to 40 

 weeks, not to be distinguished from the "natural" process, but strictly- 

 localized to the irradiated field (Lindsay et al., 1962). There also appears to be 

 general agreement that the initial damage, both in the ageing and the 

 irradiation process must be traced to the intimal elastic tissue and its 

 mucopolysaccharide matrix. The lipid infiltration is an early, or late, 

 secondary occurrence; in men it is early and very important and the relation 

 to plasmalipids, mostly measured as hypercholesterolaemia is well proved. In 

 rats (Gold, 1961) and in rabbits (our own observations) evidence points to 

 increase of hypercholesterolaemic atheromatosis by irradiation (Figs. 1, 2 and 

 3) but this may become complicated by the apparent chemoprotection against 

 irradiation by increased cholesterol (Koch and Schenk, 1961; our own 

 observations), so the time-relations between the two atherogenic processes 

 must be important. 



As we are chiefly concerned here with the initial damage by irradiation, 

 leading up to late atheromatosis; the changes in the extracellular elastic or 

 reticular fibres, narrowly related to changes in their ground substance must be 

 central. Further we have to supplement the results of measurements on static 

 material like excised "dead" aortic walls with observations of the dynamic, 

 living situation. Observations with uptake and turnover of ^^S-sulphate in 

 living animals or surviving intimal aortic tissue have demonstrated the 

 dynamic existence of the polysulphate matrix. In human foetal tissue the 

 polysulphate synthesis is high, in adult tissue it is slower but stiU indicating a 

 turnover of 1 to 2 weeks for elastic fibres. So formation and destruction of 



207 



