Serzlm Ribonuclease Activity J. C. HOUCK AND L. 13. BERMAN. From tire Surgical Researclz kfetabolic and

determination of ribonuclease (RNAase) activity, the concentration of this enzyme in human serum was estimated. A number of disease states were investigated with resnect to their effect upon the serum concentration of RXAase. Elevations in serum RNAase were collected with leucocytosis and renal disease. Evidence is presented showing that the serum content of RXAase is resultant of the elaboration of the enzyme by white cells, its renal clearance and the release of enzyme inhibitors from body tissues. ECISNTLT one of us has developed a R new, simple micromethod for the determination of ribonuclease ac-tivity (I). This method permits the quantita-tive recovery of added crystal line pancreatic ribonuclease (RNAase) from sera. Using this technique, a variety of clinical conditions have been investigated with respect to their effect upon the serum concentration of RNAase. MATERIALS AND METHODS The assay method for RNAase, described below, is based upon the fact that polymerized ribonucleic acid (RNA) will react with acidi-tied serum albumin to form a stable turbid colloid. The absorbence of this turbidity is proportional to the degree of polymerization of the anionic substrate. Therefore, a comparison between the absorbence of the initial turbidity produced by a sample of the substrate and that produced after incubation of the substrate with RNAase will provide a measure of the depolymerizing activity of this enzyme (I). The absorbence of the turbidity produced by various amounts of RNA may be deter-mined from a standard curve and the concen-tration of the polymerized substrate remaining after enzyme action may be calculated ac-cordingly. The difference between the initial and final concentration strate is then expresse