Radioligand receptor assay for urinary and serum hCG.

A radioligand receptor assay system for urinary hCG and serum hCG was developed, using 1100-2000 times g fractions of homogenates of pig testis. This method is specific for hCG and LH, and the limit of detection for hCG was 20 mIU, which could be significantly discriminated from zero at the 95% confidence level. A nonspecific inhibition reaction which exerts its influence on the assay system has been found in the urine and serum, and in performing assays for urinary and serum hCG, it was necessary to remove the inhibition reaction by diluting the urine more than eight fold or subject the serum to an extraction procedure. Since the hCG of normal pregnancy and trophoblastic neoplasia showed a dose response curve similar to that of the International Standard hCG, it became clear that these hCG could be assayed with this method. The potency ratio R/I measured by RRA and RIA of urinary hCG and serum hCG was different from those of normal pregnancy and trophoblastic neoplasia.