ISOFORMS OF CELLULAR FIBRONECTIN AND TENASCIN IN AMNIOTIC-FLUID

Amniotic fluid (AF) obtained from second trimester pregnancies present ed extradomain (ED) A, B and an oncofetal (onc-f) domain containing is oforms of cellular fibronectin (cFn) in Western blotting of gelatin-bo und polypeptides and directly of AF. Western blotting after sequential immunoprecipitation suggested at least three Fn molecules: one contai ning EDA and the onc-f domain and another minor component distinctly c ontaining all the domains, and a third one only containing EDA. The im munoblotting results for EDA-cFn and onc-f-cFn were closely similar to that for total Fn, whereas in plasma samples of normal and pregnant w omen only traces of EDA-cFn and onc-f-cFn, but no EDB-cFn, were found. Western blotting of AF also indicated the presence of three isoforms of tenascin (Tn), M(r) 190,000 and 280,000 polypeptides earlier found in many cells, and a M(r) 200,000 polypeptide, novel for AF and not pr esent in plasma. The results suggest a novel extracellular matrix poly peptide composition for AF.