Ribonuclease activity in human serum, cerebrospinal fluid, and urine

Poly(C)-avid ribonucleases of molecular weight 33 000 are present in the serum, cerebrospinal fluid and urine of humans. Purified human urinary ribonuclease was used to produce a monospecific antibody in rabbits. The antibody was capable of: (i) inhibiting the enzyme activities in the serum, CSF, and urine; (ii) reacting with antigens in the serum and CSF. The antigens in the serum, CSF and urine were found to be immunologically identical. Immunoelectrophoresis data suggested that the urinary and CSF RNAase are chemically identical. Succesful renal transplantation reduced elevated serum RNAase to normal levels. The data suggest that the most likely source of both urinary and CSF ribonuclease activity is the blood stream.