Presence of fibronectin in basement membranes and acidic structural glycoproteins from human placenta and lung.

Cold-insoluble globulin was detected in both trophoblast and alveolar basement membrane preparations, whereas it was not detected in GBM preparations. Acidic structural glycoproteins from both placental villi and lung parenchyma, which were extracted with 0.3 M acetic acid and recovered by adjusting the pH to 4.7, also contained CIg. Fractions of TBM, solubilized by either dilute alkali (0.01 N NaOH), by reduction and alkylation of the disulfide bonds, or by 0.3 M acetic acid extraction, all contained the antigen and possessed properties similar to those of ASG. The ASG fractions also reacted with antifibrinogen, but proof that the two types of determinants occur on a given molecular species is lacking at present. Purified collagenase solubilized CIg from ABM, from lung parenchyma, and from the stroma of placental villi, and this finding is strong evidence for an association of CIg with collagen in these connective tissues.