Characterization and localization of human renal kininogen

Kininogen was isolated from human urine by batch adsorption with immobilized antibody to the immunologically identical heavy (H) chains of both high molecular weight (HMW) and low molecular weight (LMW) human plasma kininogens. All releasable kinin in the guanidinium chloride eluate was associated with kininogen antigen in gel filtration fractions. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the eluate gave major stained and antigenic bands corresponding to the major form of plasma LMW kininogen. Also, the staining patterns and antigenic profiles obtained upon alkaline disc gel electrophoresis of the urinary and plasma LMW kininogens were strikingly similar. When antibody to H chain was used in an indirect immunofluorescence technique, cytoplasmic staining was observed in cells of distal tubules and c cortical and medullary collecting ducts of human kidneys. No fluorescence was observed using antibody to the unique light (L) chain of plasma HMW kininogen and no intact HMW kininogen was found in urine by radioimmunoassay. We conclude that the kidney is a source of urinary kininogen, while the L chain antigen in urine probably represents filtered degradation products of plasma HMW kininogen.