100 Albert I. Lansing 



extraction and salting. In such extracts the elastase activity 

 in vitro or in vivo is destroyed by boihng. The elastase activity 

 of pancreatic extracts persists after fat extraction and 

 dialysis. Curiously enough, although these conditions would 

 suggest that elastase is a protein, the systemic effects to be 

 outlined were obtained by oral administration of the material. 

 A unit dose per rabbit was that amount of elastase extractable 

 from 5 grams of pancreatin (Viokase, Viobin Corp., or Wilson's 

 concentrated pancreatin). 



In two groups of tracer studies using ^*C labelled acetate 

 (COOH) and glycine (CH3) with and without elastase, it 

 appears that the oral administration of this material has 

 significant effects on the metabolism of aortic elastic tissue. 

 Rabbits, in groups of five, were given • 1 mc of either of the 

 two isotopes by intraperitoneal injection and followed for 

 two to twenty-eight days. Animals were sacrificed at various 

 time intervals after injection of the glycine or acetate, the 

 aorta from the arch to the diaphragm was removed, fat- 

 extracted, reduced to elastin, hydrolyzed and transferred to 

 planchets for counting. The only difference between the 

 controls and experimental rabbits was that the latter received 

 daily doses of elastase for the duration of the experiment. 

 The data are summarized in tabular and graphic form (Table 

 III & Fig. 4). The results with the controls indicate that the 

 metabolism of elastic tissue is considerably like that of collagen 

 as established by Neuberger using comparable doses of the 

 isotopes. Every indication is that the turnover of elastic tissue 

 is very low, and indeed after administration of elastase is even 

 lower than in the control. It is difficult to propose a formal 

 explanation for this result; one possibility is that elastase 

 removes a particular component from elastic tissue, one that 

 is substantially labelled in the control. Whatever the final 

 explanation for this phenomenon may be, it is clear that oral 

 administration of elastase has an in vivo effect on the isotopic 

 labelling of elastic tissue. 



The information we have on ageing in elastic tissue in 

 human skin is much less complete than that available for 



