Partial characterization of inhibin, activin, and follistatin in the term human placenta

To determine whether the human term placenta contains inhibin, activin, and follistatin, placental homogenates from normal placentae were subjected to several fractionation procedures: 1) dye affinity chromatography; 2) hydrophobic interaction chromatography using phenyl sepharose; 3) gel filtration under acid conditions; 4) reversed phase-high pressure liquid chromatography (RP-HPLC); and 5) preparative polyacrylamide gel electrophoresis and electroelution. Purification was followed by RIA for inhibin, activin, and follistatin as well as in vitro bioassay based on the FSH cell content of rat anterior pituitary cells in culture. Two peaks of immunoactive and bioactive inhibin with differing elution patterns on RP-HPLC were shown to have molecular weights of 33K and 32K on polyacrylamide gel electrophoresis. These peaks may represent inhibin A and B. Three peaks of immunoactive activin on RP-HPLC had molecular weights of 26.5K, 25.5K, and 27K and may represent activin A, AB, and B. Immunoactive follistatin eluted on RP-HPLC as a broad peak, which on polyacrylamide gel electrophoresis consisted of three main activities consistent with molecular weights of 31K, 35K, and 38K. These studies demonstrate that the term placenta contains inhibin, activin, and follistatin, which have been partially characterized. The presence of these substances within the placenta raises the possibility of their function in local paracrine interactions.