DISTRIBUTION OF BIGLYCAN AND ITS PROPEPTIDE FORM IN RAT AND BOVINE AORTIC TISSUE

The matrix proteoglycan biglycan was identified in bovine and rat aort ic tissue by Western blot analysis and by immunohistochemistry, using polyclonal antibodies raised against peptides of the propeptide and th e hypervariable region of the rat biglycan core protein. Western blot analysis of proteoglycans isolated from bovine and rat aortas by ion e xchange chromatography and treated with chondroitin ABC lyase, with an tibody against propeptide, demonstrated core proteins with molecular w eights ranging from 43,000 to 45,000 daltons. Similar results were obt ained with Western blot studies using the peptide antibody to the hype rvariable region of biglycan, except the antibody did not recognize th e core protein of bovine biglycan. Location of biglycan within bovine and rat aortic tissue sections by immunoperoxidase histochemistry usin g the antibody raised against the propeptide revealed intense intracel lular staining of medial myocytes and endothelial cells but no extrace llular staining. In contrast, immunohistochemistry performed with the purified antibody to the hypervariable region revealed significant ext racellular staining of the adventitia proximate to the media and of th e endothelial lining but no intracellular staining of rat aortic tissu e, with no observable staining of bovine aortic tissue. These data dem onstrate that, in contrast to cultured smooth muscle cells, biglycan c ontaining the propeptide is not secreted and deposited within the extr acellular matrix by smooth muscle cells and endothelial cells from aor tic tissue.