The Physiologic and Clinical Significance of Plasma Proteins and Protein Metabolites

Circulating Protein MetabolitesThe circulating plasma proteins represent one phase in the dynamic equilibrium existing between plasma and tissue proteins. Another clinically important phase of protein metabolism in health and disease is associated with the circulating protein catabolites. These nonprotein nitrogenous substances are the resultants of intermediary metabolism of ingested and tissue proteins. The nonprotein nitrogen of the blood — that portion not precipitated by the usual protein precipitants —is a heterogenous mixture of urea, uric acid, amino acids, creatine, creatinine and a fraction designated as "undetermined nitrogen" that appears to contain polypeptides, various amino acids, adenylicnucleotide and other components. . . .