Repair in arterial tissue. Demonstration of fibronectin in the normal and healing rabbit thoracic aorta by the indirect immunoperoxidase technique.

Immunoperoxidase staining for fibronectin in ethanol- and formaldehyde-fixed, normal and healing arterial tissue is presented. Proteolytic digestion of sections fixed in formaldehyde increased the staining intensity for fibronectin in media from normal thoracic aorta and in neo-intima covered with endothelium, and had a similar effect on media from thoracic aortae with an embolectomy catheter lesion. The staining reaction for fibronectin in formaldehyde-fixed neo-intima covered with aortic smooth muscle cells was strong and almost independent of proteolytic digestion. In re-endothelialized neo-intima with a high content of proteoglycans a masking effect was observed, probably depending on poor access of immunoglobulins to fibronectin. The masking effect observed in non-re-endothelialized neo-intima with a low content of proteoglycans was much weaker. The correlation between the choice of fixative and unmasking of antigenic determinants by proteases is discussed.