Release of human chorionic gonadotropic (hCG) and its alpha-subunit (hCG-.ALPHA.) from perifused human placenta.

Abstract

The release of human chorionic gonadotropin (hCG) and its .alpha.-subunit (hCG-.alpha.) from the normal human placenta, and the effect of some stimulatory agents on their release, were studied in vitro using a perifusion system. Each perifusate was assayed for hCG and hCG-.alpha. in its own homologous radioimmunoassay systems. Both hCG and hCG-.alpha. were released from the placenta at any stage of gestation in the perifusion system. Much more hCG than hCG-.alpha. was released from the placenta in early gestation. By comparison, however, hCG-.alpha. increased gradually with the gestational age. The amount of hCG-.alpha. released was almost equal to that of hCG in the placenta in the 17th gestational wk. After the 22nd gestational wk, hCG-.alpha. was released in larger quantities than hCG, and .apprx. 10 times more hCG-.alpha. than hCG were released from the term placenta. These results were also confirmed by gel filtration of perifusates on a Sephadex G-100 column. hCG-.alpha., compared with hCG, was present in excess in gel filtrated perifusates in the last 2 trimesters. By adding 1 mM dibutyryl cAMP to the perifusion medium, the release of both hCG and hCG-.alpha. was stimulated significantly. Synthetic LHRH at concentrations of 10 ng/ml and 100 ng/ml had no effect but, at a high concentration (1 .mu.g/ml), LHRH stimulated the release of them. Moreover, mouse epidermal growth factor (EGF) stimulated not only the release of hCG and hCG-.alpha. but also their production because both hCG and hCG-.alpha. levels rose progressively with the time course in the presence of EGF. The perifusion system of chorionic tissues apparently is a useful method for investigating the release of hCG and its subunits in vitro.