Distribution of two alternatively spliced variants of the type II collagen n-propeptide compared with the c-propeptide in bovine chondrocyte pellet cultures

We have analyzed the distribution of type II collagen N‐ and C‐propeptides in the cell layers and culture medium of bovine articular chondrocyte pellet cultures. Two splice variants of the type II collagen N‐propeptide were detected by immunoblotting and immunoassay, using a new anti‐peptide antibody, while the C‐propeptide was detected using a monoclonal antibody. Type II collagen molecules containing the N‐propeptide were detected weakly in cell layers, but not in tissue culture medium of chondrocyte pellet cultures, and both splice variants were observed. Free N‐propeptide could not be detected in cell layers or medium. Type II procollagen molecules containing the C‐propeptide were detected strongly in cell layers, but not in tissue culture medium, while the free C‐propeptide was detected in both cell layers and medium. Since the N‐ and C‐propeptides must be synthesized in a 1:1 molar ratio, we conclude that the N‐propeptide is metabolized more quickly than the C‐propeptide in this system. Our model can be used to study regulation of procollagen synthesis and propeptidase activity. J. Cell. Biochem. 75:13–21, 1999. © 1999 Wiley‐Liss, Inc.