The Development of a Plasma. Volume Expander 61 



Table 1. Osmotic Efficiency of* Glutamic Acid Polypeptide in Serum 



Mix i in in Solutions 



* The osmotic efficiency of a non-diffusable substance in a solution is denned 

 as the number of cubic centimeters added to an infinite volume of the solution 

 for each gram of substance when the osmotic pressure, the quantities of all 

 other non-diffusable substances inside the membrane, and the concentration 

 of each diffusable substance outside the membrane are kept constant. 



the organisms by filtration or centrifugation, the peptide was precipi- 

 tated from solution by addition of copper sulfate which formed a green 

 rubbery complex with it. This dissolved readily in citric acid solution, 

 from which copper was removed by precipitation as sulfide or by other 

 methods. On acidification and standing in the cold a white precipitate 

 of peptide separated out. This peptide, after resolution in sodium 

 hydroxide and reprecipitation, is pure enough for physiological work. 



Molecular-weight determination by an end-group method showed 

 molecular weight of 12,000 to 15,000. By light diffraction and viscosity 

 measurements it was determined that the average molecular length 

 ranged from 150 A. to 200 A., which is of the order of magnitude of 

 serum albumin, and the molecular diameter was 11 A., approximately 

 one-third that of serum albumin. 4 On physiological testing it was 

 found that this material unfortunately was excreted very rapidly in 

 the urine in normal dogs and humans. In a human the blood stream 

 is cleared of peptide in approximately 5 hours after injection of 20 gm. 

 in a liter of saline. In a dog rendered hypotensive by bleeding, the 

 peptide solution promptly restored the blood pressure to the normal 

 level; whereupon the dog resumed urination, excreted the peptide very 

 rapidly, and urinated himself back into the hypotensive stage. 



It was obvious that, although otherwise apparently suitable as an 

 extender, this material was too small and too readily excreted by the 

 kidney to be effective for the desired length of time. Since the molec- 

 ular length was approximately that of serum albumin it seemed reason- 



