In vitro Biosynthesis of Human Chorionic Follicle Stimulating Hormone

Abstract

In order to explore the possibility that human chorionic FSH (hCFSH) may be synthesized in vitro by the placenta and secreted into the culture media, chorionic tissue of the first trimester was cultivated in the radioactive medium prepared by adding ³H-proline and/or ¹⁴C-glutamic acid. Purification of biosynthesized hCFSH from the media was carried out by a combination of Sephadex G-100 gel filtration, DEAE-cellulose chromatography and polyacrylamide disc-gel electrophoresis.
Utilizing radioimmunoassay for hCFSH, incorporation of labeled amino acid into biosynthesized hCFSH was examined. ³H-proline alone could not be incorporated easily into the biosynthesized hCFSH molecule but was predominantly incorporated into the biosynthesized hCG molecule. In a double labeling experiment with ³H-proline and ¹⁴C-glutamic acid, however, it was certified that hCFSH labeled with both ³H-proline and ¹⁴C-glutamic acid could be synthesized in vitro. Since hCFSH contains less proline and more glutamic acid than hCG, there may be a mutual relationship between the rate of incorporation of labeled amino acid into the hormones and the amino acid composition of the hormones.
In addition, on DEAE-cellulose chromatography immunoreactive hCFSH eluted at a lower conductivity than native hCFSH and its elution profile was consistent, while immunoreactive hCG eluted at a higher conductivity than native hCG and its elution profile demonstrated a considerable variation. These results suggested that hCFSH synthesized in vitro might be stable, whereas hCG synthesized in vitro might exhibit a certain polymorphism due to charge heterogeneity.