Isolation of Placental Protein with Immunological and Receptor Activities Similar to Growth Hormone

Boris Mildner* and Jasminka Marout

Laboratory of Endocrinology, University hospital »Sestre milosrdnice«, Vinogradska c. 29, 10000 Zagreb, Croatia
*Corresponding author, present adress: PLIVA d.d., Research Institute, Department of Biosynthesis and Biotechnology, Prilaz baruna Filipovića 25, 10000 Zagreb, Croatia

Article history:
Received  April 12, 1996 
Accepted June 18, 1996

Key words:
human placenta, human growth hormone, placental growth hormone, placental lactogen, chorionie gonadotropin

Summary:
It is well known that human placenta synthesizes and secretes into maternal circulation polypeptide hormones. Two hormones which have established clinical use are placental lactogen and chorionic gonadotropin. Recently, it has been discovered that human placenta also synthesizes and secretes a variant form of human growth hormone (hGH-N), now called hGH-V protein. The aim of this work was to isolate hGII-V hormone from human term placenta. The purification steps were monitored by measuring hGH as well as placental lactogen and chorionic gonadotropin immunoactivities. hGH-V immunoactivities were separated from placental lactogen and chorionic gonadotropin immunoactivities by three simple chromatographic steps. By ion-exchange chromatographies (anion- and subsequent cation-exchange chromatography) placental lactogen immunoactivities were separated from hGH-V immunoactivities. The contaminating, chorionic gonadotropin immunoactivity was separated from hGH-V immunoactivity by size-exclusion chromatography. When compared with the crude placenta homogenate, the isolated protein was purified 648-fold with an overall recovery of 0.06%. The isolated protein, M_r around 22,000, possessed immunological as well as receptor activities similar to human growth hormone (hGH-N), isolated from human pituitary.