A comparative study of the properties between human fibronectin isolated from placenta of early and term pregnancy.

Fibronectin from human early pregnancy (5-8 weeks) placenta (epFN) has been isolated by 2M urea-PBS extraction and purified by heparin-Sepharose 4B affinity chromatography followed by Sepharose CL-6B gel filtration, and compared with that of term placenta (tpFN). According to the analysis on SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and Western-blots, epFN was similar to tpFN; both are composed of two 250 KD subunits, larger than 220 KD subunits of plasma fibronectin (pFN). They reacted with antibodies against pFN and monoclonal antibodies (mAbs) raised against three mainly functional domains of amniotic fluid fibronectin (amFN), respectively. However, the affinity of epFN with mAb against heparin-binding domain was stronger than that with mAb against gelatin-binding domain; this phenomenon could not be observed with tpFN and pFN. The results of lectin-binding capacity indicated that epFN was not only distinct from pFN but also from tpFN on its carbohydrate composition. We also found there were much more FN-binding proteins in early placenta than in term placenta. The significance of these results are discussed.