Placental protein 5 (PP5)-like immunoreactivity in human urine

Placental protein 5 (PP5)-like immunoreactive material was detected in human male urine in small concentrations (17-60 pg/ml). Part of the PP5 immunoreactivity in the urine had a molecular weight of 36 000-42 500, which is the molecular weight of purified PP5 from the human placenta. In radioimmunoassay, serial dilutions of the 36 000-42 500 molecular weight material gave an inhibition curve parallel to that of the PP5 standard. The source of PP5-like immunoreactivity in the urine is not known. It may be related to urokinase, which coeluted with PP5-immunoreactive material in gel filtration.