VIII. EFFECTS OF DEFICIENCY IN ANIMALS 277 



the healed wounds or ne^^■ subcutaneous tissue was not decreased in concen- 

 tration when the animals were made scorbutic. However, the collagen con- 

 centration of the new tissue about the kidney was decreased. His results 

 led to the suggestion that the major portion of the newly induced collagen, 

 as had been previously found with organ collagen, does not need ascorbic 

 acid for maintenance. 



Perrone and Slack^^ studied the relative metabolic inertia of collagen in 

 the rat, using glycine labeled with C'' in the methylene group. Each rat 

 received 50 mg. of glycine containing 20 juc of radioactive glycine per 200 g. 

 of body weight. Animals were killed after periods varying from 1 to 34 

 daj's. The extremely low radioactivity of the glycine isolated from the colla- 

 gen indicated that the turnover rate of this protein is very slow, much more 

 so than that of the mixed proteins of muscle. The results suggested the pos- 

 sibility that "the collagen is, in fact, completely inert and that the observed 

 radioacti\dty is entirely due to the deposition of new collagen." (The ani- 

 mals were growing.) In later studies,^" also with rats, these investigators 

 deteiTnined the collagen in tendon, skin, bone, and liver in three groups of 

 rats initially ranging in weight from 50 to 70 g., 200 to 240 g., and 350 to 

 370 g. Each rat received the C'^ glycine in amounts equal to 10 nc. per 100 

 g. of bodj^ weight. Collagen was extracted, freed from other protems, con- 

 verted to gelatin, the glycine content determined, and the specific activity 

 measured. The results indicated "some metabolic activity in collagen from 

 skin, bone, tendon and liver during the first 3 weeks in young rats, very 

 little acti\'ity in old rats at any time and variable metabolic activity in the 

 'young adult' group." Robertson^^ followed with results of an investigation 

 of the influence of ascorbic acid on N^^ incorporation into collagen in guinea 

 pigs in which (a) the weight was maintained constant, (b) animals lost 

 weight because of food restriction, (c) were acutely scorliutic, and (d) were 

 recovering from acute scurvy. In general, the results showed that under 

 conditions in which the food intake w^as low there was a low concentration 

 of N^^ in the collagen, regardless of the fact that a constant amount of the 

 isotope had been fed. No specific effect of ascorbic acid was observable. 

 The results were interpreted as suggesting that nitrogen turnover in collagen 

 occurred without an appreciable breakdown of the macromolecule. 



Results of the various investigations herein reported tend to indicate 

 that the collagen turnover in adult tissues is extremely low. Although in 

 scur\'y there is consideral)le histological evidence of a partial breakdown 

 of collagen in several types of tissue, the chemical methods of estimation 

 do not reveal possible changes in its physical form. 



«9 J. C. Perrone and H. G. B. Slack, Biochem. J. 48, iv (1951). 

 '" J. C. Perrone and H. G. B. Slack, Biochem. J. 49, Ixxii (1951). 

 " W. V. B. Robertson, /. Biol. Chem. 197, 495 (1952). 



