Studies on the microheterogeneity of chorionic gonadotrophin secreted by the human cytotrophoblast in culture.
In the present study, we investigated the biological characteristics of different molecular forms of chorionic gonadotrophin (HCG) secreted by the human cytotrophoblast during its morphological and functional differentiation in culture. Highly purified cytotrophoblasts were prepared from term placentae and cultured for 24 to 96 h in the absence or presence of 8-bromo-3',5'-cAMP. Media were collected at 24 h intervals and the secreted isoforms of HCG were then separated by polyacrylamide gel isoelectric focusing (pH range 8.0-3.0) and quantified by radioimmunoassay. The secretion of HCG was significantly increased by 8-bromo-cAMP (from 23.5 +/- 6.3 ng/ml at 24 h to 1619 +/- 835.8 ng/ml at 96 h; controls, 9.3 +/- 0.1 ng/ml at 24 h and 26.6 +/- 3.5 ng/ml at 96 h, mean +/- SD). Analysis of media concentrates from cAMP-stimulated cultures by isoelectric focusing revealed the presence of several distinct peaks of HCG within the pH range of 7.3-4.8; major peaks consistently exhibited isoelectric points (pI) of 7.3-7.0 (peak 1), 5.6-5.4 (peak 2) and 5.1-4.8 (peak 3). The relative HCG content of the most acidic peak (as % of total on gel) progressively increased with time of exposure to the cAMP analogue (from 19.8 +/- 1.6% at 24 h to 34.4 +/- 4.3% at 96 h, mean +/- SEM, P less than 0.01). HCG recovered from peak 1 exhibited the highest receptor-binding capacity and in-vitro biological potency.(ABSTRACT TRUNCATED AT 250 WORDS)
Ulloa-Aguirre
A
A
Department of Reproductive Biology, National Institute of Nutrition Salvador Zubiran, Tlalpan, Mexico.
Mendez
J P
JP
Cravioto
A
A
Grotjan
E
E
Damian-Matsumura
P
P
Espinoza
R
R
D001681:Biological Assay; D002478:Cells, Cultured; D006063:Chorionic Gonadotropin / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism*; D018997:Chorionic Gonadotropin, beta Subunit, Human; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007525:Isoelectric Focusing; D009439:Neuraminidase; D010446:Peptide Fragments / Q000032:analysis; D011863:Radioimmunoassay; D011869:Radioligand Assay; D014327:Trophoblasts / Q000166:cytology* / Q000378:metabolism*
D006063:Chorionic Gonadotropin; D018997:Chorionic Gonadotropin, beta Subunit, Human; D010446:Peptide Fragments; D009439:Neuraminidase