98 Albert I. Lansing 



medial elastin or in the calcium and cholesterol contents of 

 the intima. There is a small increase in the cholesterol content 

 of the media and a thirty-fold increase in the calcium content 

 of the medial elastin. It would appear from these data that 

 the development of an affinity for calcium by arterial elastic 

 tissue is an age-conditioned process. 



It seems clear that change in composition of human 

 arterial elastic tissue, which is almost invariably associated 

 with overlying atheromatosis, is age-conditioned. That age 

 alone is not effective is attested to by the fact that the 

 pulmonary artery is normally resistant to elastic tissue change 

 at all ages. The pulmonary artery does develop typical 

 elastic tissue changes as well as atheromatosis when it is 

 subjected to stress as in pulmonary hypertension. 



In presenting these several forms of data, I have not been 

 attempting to propose that the primary lesion of arterio- 

 sclerosis is elastic tissue breakdown rather than accumulation 

 of lipid in the intima. My point is that arteriosclerosis is a 

 complex disease; at least in the human, arteriosclerosis is a 

 product of both accumulation of lipid in the intima and 

 degeneration of elastic tissue in the media of arteries. The 

 question is: Is there a common basis to both of these lesions 

 or is their occurrence coincidental? I suspect that the former 

 possibility is valid and that the material called elastase may 

 be implicated in both elastic tissue and lipid metabolism. 

 The data are far from complete and elastase is as yet poorly 

 defined but sufficient experimental data are available to 

 warrant serious consideration of the role of this material in 

 arteriosclerosis. 



Elastase, exclusively extractable from the pancreas, was 

 originally prepared and characterized as an enzyme by Balo 

 and Banga (1950). It is apparently specific for elastic tissue 

 and acts upon the substrate to convert a fibrous protein to 

 the globular form; in solubilizing elastic tissue there is no 

 apparent release of peptides or amino acids. In this labora- 

 tory elastase has been used to work out the fine structure of 

 elastic fibres. The enzyme solubilizes both elastic fibrils and 



