Abstract
When immunological measurement of a protein hormone is desired to be introduced into the clinical field, the antibody-antigen system has to be highly purified. The authors attempted to purify human placental lactogen (HPL) by combination of Sephadex gel filtration, DEAE-C chromatography and DEAE-Sephadex A-50, and succeeded in obtaining a highly purified HPL preparation which shows a single band on 7% polyacrylamide gel electrophoresis and is not contaminated with non-effective protein on immunoelectrophoresis. Anti-HPL-serum was made using this HPL, which showed no cross reaction with human serum protein.
Employing the above antigen-antibody system, the authors measured serum HPL of pregnant women at every stage of gestation by radioimmunoassay (RI). But, as a special apparatus and a complicated technique were needed for radioimmunoassay, Authors attempted to establish a clinically easier immunoassay of HPL by introducing single radial immunodifusion (SRI). The optimal conditions we finally decided for SRI are; antibody concentration, 1%; the thickness of the agar plate, 1.2mm; diameter of the well, 4mm; the amount of antigen placed, 10 μl. The regression coefficient was 5.48 and HPL over 5 μg was detectable. HPL values obtained by RI and SRI were almost identical. This SRI method made it much easier to measure serum HPL of pregnant women, and to observe pregnancy course from the view point of placental function. Furthermore, it may present an important clue in differential diagnosis between normal pregnancy and trophoblastic neoplasia by combination with measurement of human chorionic gonadotropin (HCG)
